How to Weigh Pigs w/ String


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.

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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:

  1. 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.
  2. 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.
  3. 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.
  4. 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 where the horns attach – this is called the poll. 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.
  5. 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!
  6. 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.
  7. 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.

Lard vs Bacon Pigs can be assessed by the ratio of L to G. L is the length and G is the girth of the pig. The ratio of these numbers on a finisher pig in good condition (not skinny, not fat) is a fair indicator of Lard vs Bacon breeds. If L>=G then it is probably a bacon / meat breed. If G>>L then it is probably a lard breed. See Lard vs Bacon Pigs” for more details.

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:

(66″ x 68″ x 68″) ÷ 400 = 762 lbs

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.

Hw = 72% Lw

Where:
Hw is Hanging Weight
Lw is Live Weight

Assuming scald & scrape, skin-on, head-on, trotters-on, tail-on.

Cw =67% Hw

Where:
Cw is typical commercial cuts.

This will vary with bone-in, bone-out and how you cut the pig. That ~30% between Hw and Cw is oddments and good eating low-on-the-hog.

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.

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

Also see Measuring Pigs with a Stick.

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About Walter Jeffries

Tinker, Tailor...
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88 Responses to How to Weigh Pigs w/ String

  1. Nancy says:

    I used your string formula on my 5 month old and it came out just over 100# – I figure the lighter weight likely due to her being 1/2 guinea hog (other half Berkshire). I don’t see her getting to 220 in another month so I’m thinking of letting her go to 7 months and that’s it. She has good irrigated pasture with clover and alfalfa and is fed lots of veges but little anything else. Thoughts?

  2. Yvonne Jett says:

    My pig is 40″ long and 41″ girth, I come up with 168.1 but I went to a show yesterday and she weighed 213. What am I doing wrong?

    • Learning how to do the measuring is probably the issue. Take a look at the position of the pig and check the description text. You want to go from the poll to the base of the tail where it attaches to the butt. The girth is the heart girth behind the front legs. Your numbers look like perhaps the length got under measured and should be a little longer as we almost never see a pig where the girth is greater than the length but that can be a breed or condition specific issue too. Practice.

  3. Amy says:

    The information is great.
    The humor is even better!

  4. cherry says:

    what is the exact weight of 135 days old pig?

    • That would rather depend on the breed, sex, genetics, season, climate, health and diet of the pig. Exactness is not.

      Might be somewhere in the range of 50 to 200 lbs depending on all those variables. Measure the pig and the formula will give you an estimate.

  5. Stephanie Hughes says:

    I’ve used this formula to guestimate weights on dogs, cats, even a rat (all animals measured with heads down curved back)… and it seems accurate +/- 1-4lbs (weight confirmed on veterinary scale to confirm) This helps wonderfully when I don’t have a scale and need to select flea topical sizes for my pets.

  6. Farmerbob1 says:

    Walter, if you ever wanted to put together something that would measure weight of even the biggest pigs with reasonable accuracy, you could just use a platform with a substantial pneumatic cylinder on one end. Stick a well-graduated air pressure sensor in the cylinder.

    With the pig off the platform, zeroize the sensor. Pig steps on the platform, record the pressure. The pig gets off the platform, and you get on. Record your pressure. Go weigh yourself on a human scale. Do simple ratio math, comparing your weight and pressure to pig pressure and unknown weight.

    Viola! Super-easy scale that’s reasonably accurate, and even works if it’s a big rusty or dirty, since you are using your own weight as a control.

    • We plan to. The issue is we need to have multiple scales because there are separate herds and some of their members never cross over. We don’t have indoor barn areas for it. With our climate it is difficult to have something like this six months of the year because of ice and snow. This makes even simple moving things like gates challenging in a way that people who live on land can’t understand. Our surface raises and lowers by about 4′ over the seasons.

      What I will probably do is build it into the stun pen of the Abattoir. Almost every pig eventually passes through those pearly gates.

      In the mean time I am able to get within a few pounds using a string or a stick. Good enough as my good friend Boris would say.

  7. Jack ruby says:

    Getting 2 new pig 50 lbers. Can’t wait to fatten them up and try this string measuring technique. I’ll try it when i think their close to 200lbs and see how close I guessed. Thanks for the tip

  8. Jack ruby says:

    Does anyone know how to use safeguard pellets wormer for 50lb. Pigs , I just got them . How much do I mix with their feed . I have 2 pigs. The instructions on the bag aren’t really clear. Need some advice for daily rations of wormer for 2 pigs like a half of cup per 50lb. Bag of feed for example, not sure how to mix proper amount with feed. Please help . Thanks

  9. Circ says:

    “(In the photo she was in the 2nd trimester.) ”

    LOL “as useless as teets on a boar!”

    • “as useless as teats on a boar!” is an interestingly wrong phrase. High teat counts on a boar are critical because they indicate how his daughters will be. More teats produces more milk produce more large weaned piglets per sow per year. We’re up to 18 now in some of our lines. Our baseline is 14 which is above the industry average of 12.

  10. Julia McKeon says:

    Hi Walter, greetings from Danby, VT! I love reading your articles, they are so informative and have been very helpful for us in raising pastured pigs. I wanted to let you know that we tried this method of weighing pigs with string the day before they were processed, and it was pretty accurate! Our heritage breed mix gilt was weighed with string to be about 360 lbs, her hanging weight was 269 lbs so working backwards we calculated she was close to 350 lbs live weight. Our Berkshire barrow was weighed with string to be about 210 lbs, hanging weight was 174 lbs which worked out to be about 220 lbs live weight. Thank you so much for providing us with a relatively accurate way to weigh pigs!

  11. ioi says:

    I found when using the string method, that if I didn’t reach under the pig to do the girth measurement, they were more cooperative. I’d lay the string out in front of them, and get them to step over it while I held the ends and then get a snug measure before moving on to the length. The girth measurement seemed easier because it was more consistent. Depending on how high or low the pig’s head was, the length measurement would change quite a bit and no matter how much I looked online, I could never tell which head position was best for getting the length measurement. Usually I’d measure the length a couple of times and just average it to get the number for my calculations.

  12. Jessica M. says:

    Ok. I have got to be doing something wrong, here. I measured my kids’ 4H pigs just about 20 minutes ago on this method. Our neighbors and such estimate their weight at around 160-180.. I went out, did the measurements, and this is what I came up with. I can tell just by looking at my girls, they’re no 60 pounds! LOL!

    What am I doing wrong here?

    #199(aka Alice)
    (25L x 26G x 26G) / 400 = 42.25 Lbs

    #200(aka Suie)
    (31L x 28G x 28G) / 400= 60.76 Lbs

    I’ll reread the article again. I had a measuring tape for tayloring, that shows inches.

    • Jessica M. says:

      Now, these are show pigs, so I don’t know if that matters. The have larger shoulders and wider rumps.. like I said, if that matters.

    • Measuring a pig is a learned skill. The position of the pig is important – look at the photos in the article. The most common mistake is getting the Length wrong because the pig’s head is too high or low or you measure from the wrong spot.

      With our pigs it is normal for the girth and length ratios to be very similar to what you measured so that makes me suspect you got your measurements reasonably close.

      That said, your math is spot on. If these pigs are only 25″ and 31″ long then they are more likely closer to your calculations than to your neighbor’s estimates.

      I would suggest repeating the measuring process ten times to find out what your variance is. This is a good lesson in scientific method for your kids. You can teach about statistical deviation as well as good technique.

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