Weighing a pig is a tricky thing. When they are small, say under 50 lbs it is easy. You just pick them up, step on the scale to get your combined weight and then do a little math to get the piglet’s weight. Hopefully you still have your hearing as they can squeal quite loudly.
Above 50 lbs that gets a bit more challenging. I’ve weighed pigs up over 100 lbs that way but I would rather not. I’ve come up with all sorts of ways of building a pig scale but the truth is I rarely need it so it hasn’t become a priority. Perhaps I never will.
When they are as big as Big Pig, pictured above, it would take a very serious scale indeed. Fortunately she is so nice that she would probably cooperate if I ever got around to building something big enough to do the job.
There is an easier way – a simple method of getting an approximate weight on a pig using a tape measure. I actually use a piece of string to do this as it is softer, quieter, doesn’t bother the pigs like a steel tape would and is handy to carry around in my pocket. If necessary I can simply knot the string to mark the weights and then go measure the string later.
But you say with indignation, strings measure length not weight! Well, yes, but pigs have a certain amount of similarity to their structure so a little bit of clever and very simple math turns the lengths into volumes into weights.
How to weigh a pig with a string:
- Get the trust of the pig – This is critical. Uncooperative pigs not only make the process more challenging but they can bite. Don’t try this with some random pig you meet on the street and likewise don’t go hopping over a fence to measure someone else’s pigs. Even with your own pigs don’t expect to get their trust all in one fell swoop. Over time, especially during feeding, interact with your pigs. Pet them as they eat. Rub them behind the ears and on the back. Let them learn to like being touched by you. To do the measuring you’ll need to reach around the pig so they need to trust that you’re not up to get funny, even if you are.
- What you’ll need – Besides the string you’ll also need some other things to do this easily:
- Piece of string about 60″ long – A piece of baling twine works well. Always save those hay bale strings. They wreck havoc with tillers and other rotary equipment if left on the ground and they are useful for measuring pigs, tying up fences, holding shut gates and such – so keep track of them. A 60″ (150 cm) size works well for piglets, weaners, growers and finishers up to 300 lbs (136 Kg) or so. If you’re doing a big pig, like Big Pig pictured above, then you’ll need a longer string – think 75″ (187 cm) or longer.
- Measure – A tape measure laid out works well. For smaller pigs a yard stick or 4′ stick works well. By the time they get to be finishers though you will be dealing with 48″ to 60″ for some of your measures – at that point a yard stick works but you have to double the string or measure twice.
- Notepad and pencil – To write down the pig, length and girth. Leave another column for the final estimated weight for each pig.
- Food – For the pig, not you! If you dump some nice treat on the ground the pig is going to be a lot more tolerant of you taking its measurements.
- Approach the pig – Be calm. Don’t rush in. Talk to the pig. Be normal. Be yourself. Take your time. Don’t rush her. Offer her a drink. Give her something to eat. Then when she’s distracted try rubbing her shoulders a little. Let her get relaxed and used to you before you make your move and start putting your arms around her in ways that might be misconstrued.
- Measure the pig’s length – Put one end of the string just above the top of the tail where it joins the pig’s butt and then stretch the string above the pig to the crown of the head between the pig’s ears. You don’t need to actually touch the pig in many cases but if its back is curved then lay the string down onto the pig’s back. Do get the string tight to get a good measurement. I do this measurement first as it is the least bothersome for the pig. I then loosely knot the string to indicate that length and thus saving it without having to stop to measure the string right then. This is where a tailor’s cloth measure would be handy.
- Measure the pig’s heart girth – Stretch the string out between your hands and wrap it around the pig just behind the front legs. Get a tight measure without bothering the pig too much. Give it a good ol’ hug!
- Log your measurements – Again pulling the string tight, measure the string to get the pig’s heart girth. Write that down along with the pig’s name. Then measure the string to the knot and get the pig’s length. Write that down.
- Unknot the string – Get the string ready for the next pig or put it back in your pocket so you don’t look so threatening. I do not suggest a kiss at the end of your date but that is up to you.
Once you’ve got the measurements on all your pigs you can sit down and do the math. It is a very simple formula:
Weight (lbs) = (L x G x G) ÷ 400 (inches)
or
Weight (Kg) = (L x G x G) ÷ 13781 (cm)
where
L = Length
G = Heart Girth
Do note that on large pigs, over 300 lbs or so, this tends to over estimate their size by a few pounds. On small pigs, say under 50 lbs, this method tends to underestimate their weight a bit. However the method works very well for grower and finisher pigs which covers the most common times you actually might want to check a pig’s weight.
Interestingly, this also works for dogs although it tends to get the weight just a little high based on our guardian dogs. It might be their thick fur. On the other hand it does not work on me. According to this formula I am only 158 lbs when in reality I’m more like 185 lbs. I guess I’m just dense.
So, just how big is Big Pig? Well, you never ask a lady her weight. Fortunately, Big Pig is very friendly and quite cooperative. I didn’t even have to wine and dine her to get her vital stats. Her measurements come out to be: Bust size of, er, I mean heart girth of 68″ and length 66″. A perfect Yorkshire sow. Doing the math that gives us:
Wow! She’s bigger than I thought! Her excuse is that she is in the third trimester of her pregnancy so she’s carrying a little extra weight. (In the photo she was in the 2nd trimester.) I was polite and told her that it really didn’t show. Truth is that weight estimate might be a little high as she has just barely started to bag up which throws her up a bra size and a few inches for the girth. Fortunately she’s not all that sensitive about her size. After all, she is Big Pig.
Fine Print: This is probably not as dangerous as bungie jumping but pigs can bite, step on your feet, crush you, etc. Strange pigs probably will bite. You do this at your own risk and hopefully only with your own pigs. Use only under parental supervision. Don’t try this at home kiddies. Size and color may vary. Limited availability of some models. Not sold in stores. Void where prohibited. No walking on the grass when voiding.
“A pacifist is someone who feeds the alligators hoping that the alligators will eat him last.” -Winston Churchill
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Tags: howto DIY weigh pig math
Hm a date with a pig. I will remember to take a string. :-) Verry funny walter!
This reminds me of when Wayne did a “simple calculation” to plot the location of all known asteroids between Mars and Jupiter.
Neat! Seems easier than trying to lure a pig onto a scale and making them hold still long enough to read the weight. (Based on how little my dogs enjoy that.) I wonder if it would work on a sheep? I suppose on a freshly sheared sheep. My guess is the doesn’t work as acurately on humans because we 2-leggers have more proportional weight in our legs and that throws off the calculation. I wonder what would happen if you measured your length down to the mid-thigh or knee area.
I’ve also seen this done on horses too. Pretty cool! Like you said the weight can be off some, but sure is easier than trying to pick-um up. Love all the pictures. My kids think you raise wolves-by the way. Keep up the great posts.
That’s very funny, Walter. I was cracking up.
Informative and very entertaining!
When you measured yourself, did you measure only to the base of the neck, or all the way to your crown between your ears?
OTOH Sarah is probably on to something with her observation of weight distribution on bipedal mammals.
Big Pig has a lovely curvaceous figure!
I measured from my tailbone to the crown of my head. Seemed like that was the best approximation. We’re flatter than pigs. They’re more barrel shapped. I think I would need to adjust the constant (400) to something else to make it work better for people.
What great information!
We use a weigh tape on our goats—same general idea, I guess, except you buy it for the purpose, and instead of inches on the tape, it has pounds.
I remember getting shafted on purchasing a feeder steer a similar way. The crafty old farmer “sold” him to me at weening, but didn’t collect any money–said give im a while to get used to being weened. . . .About a month later he got out his chart and string and charged me by weight. Ouch. That was one fattened calf!
Thanks for reminding me of this practical method. I’m thinking of getting some baconers soon.
hi wow! has your site helped us termendously! we are first time pig owners and i sure appreciate all this great info, heres my comment well it’s really a question. just when is it time to slaughter the pig? we have two, one we are going to breed and one we are going to eat. should we eat the smaller one or the larger one? sure would appreciate your advice. andrea
Andrea, The best time to slaughter a pig is when you are ready to eat it. Seriously.
Commercially pigs are generally grown to 225 lbs or so because now a days people want smaller hams and at about that size the rate of conversion of feed to meat starts to decrease.
For home slaughter, it is just as easy to slaughter a 300 or 400 lb pig as it is to do a 225 lb pig. If you are having someone else do it they usually charge the same rate for either. Thus you might as well go for a larger weight, especially if you are pasturing the pigs which means your feed costs are not as critical.
I like doing slaughter in the cool of the fall best of all. There are no flies and the weather is right for hanging meat without a refrigerator. As you get into late fall and winter pasture gets low so that fits as well.
Additionally, a great way to keep meat fresh is to keep it on the hoof. Once you slaughter and freeze or can the meat the quality starts to degrade. Putting off slaughter not only lets the animal get larger but means that the meat is fresher when you really need it.
The last thought is that realize not all female pigs are fertile. In the industry about 75% are fertile. So what you might want to do is breed your two pigs and then if one does not ‘take’, that is to say get pregnant, slaughter and eat her. Hopefully the other will produce piglets for next year’s meat.
On the down side, some breeds of animals, especially if they are grain fed, will start putting on more fat than meat at some age. You probably want to slaughter before that. With pigs on grain it is around 300 lbs that this tipping point is reached. On pasture I don’t see this happen – even our 700 to 800 lb sows are in excellent condition and the boars never get fat unlike confined hogs.
Short answer: when you need the meat or lack the feed it is time to slaughter. Typical slaughter weight is about 225 lbs which is generally about six months of age or about 45 inches (Girth & Length each).
Very cool observation Walter.
When I go out to pick pigs each week to decide who to ship and who to keep I pre-calculate the lengths I am looking for which speeds up the process. e.g., I want a 42″ roaster, a 50″ finisher, etc.
Note that the G factor, Girth, vs the L factor, Length, is very important. Different types of pigs have different ratios. We have been breeding for bacon pigs so our pigs’ L is greater than their G – long pigs. With a chuffy or fat pig G comes to dominate. Last week I took one pig that the ratio L=2G. That’s a long pig indeed. Lots of bacon and chops. The butcher sees them come in and calls them mile long pigs. My wife calls them choo-choo train pigs.
Thank you! I have been surfing to find out how to tape a pig and you are the only sight I have found (so far)!
A question: The length measurement varies depending on whether the pig’s back is curved (eating a a trough) or straight, sometimes as much as 2-4 inches. Which measurement should I take?
I use the walking position like shown in the position above. I had a pig this morning that only wanted to be measured with his head up. It makes about a 2″ difference which is about a 4% difference or about 10 lbs in the estimated live weight compared with the way Archimedes is in the photo vs head up for a typical finisher pig. That only comes to a difference of about 5 lbs in the final cuts which is only a 2% variance.
Do remember that this is an estimating tool. If you can be accurate to within 2% you’re doing great! :)
Thank you so much for this simple calculation. We’re raising 3 feeder pigs, and this is our first experience with them. We wanted to be sure that they were of a good weight to slaughter, because I’d read that the take home meat to live weight ratio improves considerably for a 200-220 pound pig vs a 150 pound pig. They are now about 6 months old; however, I had no clue how much they weighed. Your formula puts them in the 230# range, which is just what I wanted to see. Thank you for sharing.
This also works with structural steel but I think I’ll continue to use my 70′ 120,000 pound commercial truck scale.
If you;re ever in North Carolina and need to weigh a pig then feel free to use my scale. I’m certified as a weighmaster by the NC Department of Weights and Measures which is a subdivision of the NC Ag Dept.
i love bacon aand i wish they kill more pigs
When you multiply LxGxG/400, what does the 400 stand for?
We go to a restaurant supply house to purchase our meat, but there is no scale until the checkout. This will really come in handy and puts us within a dollar of what we are willing to spend. Thank you so much for posting this info!
The 400 (or 13781 in metric) is just an applied constant that transforms the volume to weight. Like saying x=5y where 5 would be the constant.
How did you arrive at the number 400 for the constant?
thanks for the formula. I weighed my pigs today – 118lbs and 115lbs in just over 3 months old. My big guy, Bacon, would be a fine one to breed with 9 tits on each side, solid as a rock and good natured.
somebody has boobed with their conversion; 400 inches is equivalent to approximately: 1,016 centimeters.
Bill, the formula conversion to metric adjusts for both inches-centimeters and pounds-kilograms. This is why the constant comes out differently than you expect. Run some numbers through the formulas and play with it and you'll see it works.
Does this work well with estimating the amount of feed to give a gilt during her gestation period?
Probably. We free feed pasture/hay and whey so I have never used it this way. I use the measurement method primarily to figure out if pigs are big enough to take to the butcher.
I just measure my pigs and they are 27kg. There about 3 months old now. That seems underweight. What do you think? Should we be feeding them more?
Rowly, Is that the actual age of your pigs or is that the days since weaning or is that the days since you got them? 27 Kg is about 60 lbs, for those of us who use the other system of measures. The breed also makes a big difference as some will grow larger and faster. For example, Yorkshires, which are the basis of our herd are big boned, fast growers and large. Tamworths which we have a little in our herd are not so fast or big. On the extreme small end are breeds like the Pot Belly pigs. Note that a fattier pig will actually be a little lighter than the tape shows since fat is lighter than muscle. Short answer: your pigs may be a reasonable size for 3 months of total age. Look at their condition and how their putting on muscle. In another comment you had mentioned they were on a high bread diet so my guess is they are a bit fat and you may want to boost the protein, especially lysine, in their diet. Full access to greens, that is pasture, is very good.
Thanks for your answer. Very helpful. Have talk to a local supermarket and will be getting old diary products tomorrow. Our pigs are westessex saddlebacks. They start off in 200m2 pasture, but by the end are in 200m2 of dirt. At some point they change from growers to finisher. At that point i should feed less bread and mre diary is that right?
Actually, it is the opposite. The growers need higher protein levels than the finishers, if you are going to track that sort of thing exactingly. We don't. Ours are out on pasture and get free access to the dairy. Pasture/hay makes up about 90% of their diet and dairy about 7% of their diet. The remaining three percent is mostly apples, pumpkins, turnips, beets and other things we can grow – very seasonal. On occasions we get bread from the local baker – most of this gets used as a training treat for loading. Once in a while we get boiled barley from a local brew pub – almost all of that goes to our grower pigs since it is so high in protein. I would love to get more of the barley but the supply is very limited. Check your local brew pubs.
This has really helped me out! I recorded our boar’s weight and put the video on YouTube at http://www.youtube.com/watch?v=n1SFCkjUjZ4
Thanks!
David
One new trick that I’ve been using for a couple of years is most of our pigs are cubic, that is to say, their girth and length are within about 2″ of each other at finisher size. Using this knowledge I use a stick and just lay it along their backs to pick pigs as we sort. If a pig is particularly long or short, greatly different than the others, this does not work.
Great trick! I love little things like this that make farming and life easier. Messing with a scale would be too hard.
Does anyone know how to get the weight of a hog by the weight of the head? My Husband has said it can be done but does not know how. He says you have to multiply it by something and we can not find it anywhere. Please help if you can.
Thanks!!
Interesting thought. I’m not sure. I haven’t kept careful track of this although I may have the data that would let me figure this out. From sort of watching cuts go by I would say that the typical head of a 220 lb live weight pig is about 12 lbs so multiplying by 20 is a rough guess. Some complications would be: 1) is the jowl, ears and neck meat on? 2) How high on the spine was the head cut off? 3) Is the pig of the dish shaped or straight nose variety? 4) Some pigs have much longer noses than others. One might also need to do some adjustment for age as the bones harden at older ages adding weight. Not sure if that would be proportional or not.
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does the string measure technique work on lactating sows or does their engorged teats throw of the result? seems that right behind the front legs isn’t actually engorged but rather close to the breast bone there. looking for means of evaluating our sow’s condition beside my new eyes . thanks!
If where you’re measuring has bagged up tissue then yes, it will throw the calculation.
For evaluating look along her spine. If you see too much fat she’s fat. If the spine bones are showing then she is peakid, too skinny. Too much jowl wiggle can be another sign of fat.
Hello! Thanks for all the wonderful information. I’ve been reading your blog for three (full!) days now. :-)
I am so happy that I read about your 9-patch intensive rotational grazing before getting my piglets next the spring.
My question is: how do I know if I am giving my pigs enough grain? They will be on pasture, but our pasture is not awesome (hoping the pigs will help us get ready to redo the pasture.). It is low nitrogen soil with brome grass and small willows. I am quite sure that we will need to supplement, but grain, hay, everything, is very expensive up here. (I am in the Yukon, next to Alaska).
I know that in one of your posts, you talk about giving pasture only, and that it takes longer for the pig to gain the weight. As we have a very short season (snow on the ground already, and the garden has been frozen over for a month and a half now), I can’t really take the “wait and see” approach.
So, any estimate of how much pig grain I should give my guys? Any way to know, as I go, if I am feeding them too little? Also, can you free-feed a pig grain, or will they eat it instead of the pasture that they are on?
Thank you so much.
Get a copy of the book “Small Scale Pig Raising” by Dirk van Loon. It is an oldie but a goldie. In that book he has tables for grain feeding based on different ages – it changes as they grow. Pasture the pigs during the day and then feed them the grain in the evening. That way they maximize their use of the pasture and supplement with the grain.
As to your pastures, start planting protein. Legumes pull nitrogen out of the air giving you free fertilizer. This becomes readily digestible protein. If you can supplement with dairy (e.g., whey, milk, cheese, etc) so much the better.
Next, observe the pigs and score them. This is something that takes some getting used to but you can do it and fairly quickly. They should have good muscle development, a think layer of fat and not be overly fat. See Body Condition Scoring for more on that.
I would not suggest free feeding a pig grain unless you have really deep pockets.
Thanks so much for your answer.
I already have “Small-Scale Pig Raising” on order. :-)
We can plant peas, but they may or may not actually get filled-out pods before they are killed by frost. Would they still be a useful crop for pigs even if they don’t have peas in the pods?
We can’t grow pumpkins here. :-( But we can grow turnips and beets if I cover them at night, or grow them under remay cloth.
I found a butcher today. :-) He will make bacon and hams. Very exciting!
Plant what ever works with the timing, temperatures and light you have. The pigs love the turnip and beet greens, later they eat the tubers.
I used this measurement to estimate the weight of my pig (girth = 36″, length = 33″) which gives an estimate weight of 107 pounds. My pig actually weighs 185 pounds (measured on a grain scale accurate to .2 pounds). She is by no means lean as her jowls wiggle well and her gut is very full of fat and barrel shaped. I feed her deer guts and bones about once a week and always has corn and fruit/nuts available 24 hours. She lives in a horse trailor and loves my company. Any idea for the variation from the calculation?
One possibility is that you didn’t get a good length measurement. That is short of such a large girth. Based on those measurements she is a very fat pig so that may be the reason she doesn’t follow with how it works for us. On our pigs the length is great than the girth. You may want to look at condition scoring to figure out if she is over weight and cut back on the calories in her diet. If she is overly fat you’ll end up with a lot of fat. That is not necessarily a bad thing if you like rendering lard – something we use in our cooking. There are some breeds which are known as lard type which do have very large girths and lots of fat. What breed is your pig?
Works for me! Thanks for this tip. I had two hog gilts going to market and have been tracking their progress. This was only about 3 pnds under. Very close.
Excellent. The trick worked for me on our pigs. We just got the meat back and it is sooooooooooooooo good!
I visit this website every year for a refresher on “how to weigh a pig with a piece of string” Very accurate and a great refresher. Thank you for a great website
Hi, Walter
I was hoping you could help me out in guessing how long my pig will be by the time they reach 220lbs. We are going to be rotationally grazing our 5 little weaners with electric netting. We are trying to build them a moveable house to travel with them, but we have no idea how big we need to make it to still house these 5 pigs in October when they are 220lbs each. Can you help us out with dimensions that would be appropriate?
Thank you so much!
Shari
As a general rule it is about six months to 250 lbs but that varies with diet and breed. We breed for rapid growth on pasture/hay+whey as the primary diet. A pig that was designed for a corn diet would not grow as quickly on our management practices. Our pigs on just pasture take a couple more months to get to slaughter weight.
I figure on one acre per ten pigs as a sustainable pasture rate. Again, that will vary depending on how good the pasture is and what else you’re feeding. Plant legumes such as alfalfa and clover which are high in protein. Pumpkins, sunflowers, turnips, beets, kale and rape are all good fall feed too.
With the netting, simply observe when they have eaten down an area to a few inches in forage height. Then move them.
Hi, Walter
Thanks for the info about the pasture size. What I was really wondering about, though, was how big to make the little pig house that will travel with them from pasture to pasture. (I assume they will only be in there to sleep, or if it gets really cold/windy/rainy.). Will a 6′by8′ shelter fit five sleeping 250 pound pigs?
Thanks!
Pigs tend to sleep in a pig pile, even in warm weather. I suspect all five of yours will sleep touching. At finisher size figure six square feet per pig so about 30 sq-ft for sleeping or about 5′x6′. 6′x8′ makes for a little extra room.