Estimate a pig’s live weight in kg or lb from heart girth and body length measured with a tape, or from heart girth alone, plus its hanging weight.
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Pig Weight Formula
A tape-measure estimate of live weight uses heart girth and body length, with both measurements in inches and the answer in pounds:
- Where PW is the pig weight (lbs)
- HG is the heart girth (inches), measured as the circumference of the pig directly behind the front legs
- L is body length (inches), measured along the back from the midpoint between the ears to the base of the tail
Washington State University Extension describes this two-measurement estimate as less accurate than a scale. The calculator retains the unadjusted divisor of 400. Girth-only mode uses PW = 10.1709 × HG − 205.7492 in pounds and inches. Its missing-girth solver, and the two-measurement missing-girth and missing-length solvers, are algebraic rearrangements, not independent measurements. Unit conversion uses exactly 2.54 cm per inch and 0.45359237 kg per pound (NIST).
Formula Accuracy and Limitations
The Kansas State study fitted the girth-only equation to 100 growing-finishing pigs weighing 50–273 lb and reported R² = 0.98 with a study-specific ±10 lb interval. A commercial-farm validation agreed, but show pigs after transport and restricted feed or water were underestimated. These findings do not establish a universal error bound or validate a 3% accuracy claim for the separate girth-and-length formula.
In the girth-only equation, a 1-inch girth error changes the estimate by 10.1709 lb; the sensitivity of the two-measurement formula also depends on body length and girth. Results outside the fitted 50–273 lb range are extrapolations. Neither equation establishes a breed, age, body-condition or carcass-yield adjustment. Use a suitable livestock scale when an accurate live weight is needed.
Measurement Tips for Accurate Results
Use a flexible tape with the pig standing still and its head level with its body. Measure heart girth snugly just behind the front legs, without compressing the body. Measure body length along the back from between the ears to the tail base. Average three girth readings. Keep normal continuous access to feed and water; the K-State equation was unreliable after transport or restricted intake.
Average Pig Weight by Breed
Breed alone is not an input to either equation. The calculator does not infer an adult sow or boar weight, or apply a breed-specific multiplier. Each listed animal still requires individual measurements or a scale weight:
| Breed | Sow Weight | Boar Weight | Model Adjustment |
|---|---|---|---|
| Yorkshire | Not inferred | Not inferred | None |
| Duroc | Not inferred | Not inferred | None |
| Hampshire | Not inferred | Not inferred | None |
| Berkshire | Not inferred | Not inferred | None |
| Landrace | Not inferred | Not inferred | None |
| Chester White | Not inferred | Not inferred | None |
| Spotted | Not inferred | Not inferred | None |
| Poland China | Not inferred | Not inferred | None |
| KuneKune | Not inferred | Not inferred | None |
| Pot-bellied | Not inferred | Not inferred | None |
| Large Black | Not inferred | Not inferred | None |
| Mangalitsa | Not inferred | Not inferred | None |
A breed label does not resolve individual differences in conformation. Do not add an undocumented breed, sex or body-condition correction to these equations.
Pig Weight by Age
The calculator does not predict a growth curve from age. The ages below are checkpoints for recording an individual animal, not weight targets or feeding recommendations:
| Age | Weight from Age | Age Adjustment |
|---|---|---|
| Birth | Not inferred | None |
| 1 week | Not inferred | None |
| 3 weeks | Not inferred | None |
| 6 weeks | Not inferred | None |
| 8 weeks | Not inferred | None |
| 10 weeks | Not inferred | None |
| 14 weeks | Not inferred | None |
| 18 weeks | Not inferred | None |
| 22 weeks | Not inferred | None |
| 24 – 26 weeks | Not inferred | None |
To assess growth, compare repeated scale weights over a measured interval. An individual tape estimate does not establish an expected daily gain, a temperature response or a growth difference between management systems.
Feed Conversion and Cost to Reach Market Weight
Feed conversion ratio is feed consumed divided by live-weight gain on the same weight basis. These live-weight equations do not predict feed conversion or feed cost; enter measured feed use and actual costs in a separate budget.
As a hypothetical arithmetic example, a gain from 15 to 280 lb is 265 lb. An assumed feed-to-gain ratio of 3 would imply 795 lb of feed; an assumed price of $0.20/lb would make that feed cost $159. These are illustration inputs, not performance benchmarks, current market prices or recommended target weights.
From Live Weight to Retail Meat
Understanding the relationship between a pig’s live weight and the amount of retail meat it yields is essential for anyone raising pigs for meat. The conversion happens in stages, and significant weight is lost at each step.
This calculator estimates live weight only. It does not calculate hanging carcass or packaged-meat weight. Those quantities need separately defined processing weights and yields; no dressing percentage is applied to the result.
Ask the processor which parts and processing stage are included in each quoted weight. Do not interpret the live-weight estimate as the amount of saleable or take-home meat, or apply an unsupported breed-based yield factor.
Heart Girth to Weight Reference Table
The values below are calculated from PW = 10.1709 × HG − 205.7492 and rounded to two decimal places. Asterisks mark estimates outside the 50–273 lb weight range used to fit the K-State model:
| Heart Girth (inches) | Estimated Weight (lbs) |
|---|---|
| 25 | 48.52* |
| 28 | 79.04 |
| 30 | 99.38 |
| 33 | 129.89 |
| 35 | 150.23 |
| 38 | 180.75 |
| 40 | 201.09 |
| 42 | 221.43 |
| 44 | 241.77 |
| 46 | 262.11 |
| 48 | 282.45* |
| 50 | 302.80* |
* The 25-, 48- and 50-inch rows are extrapolations beyond the fitted weight range, not validated predictions. More displayed digits do not imply greater biological accuracy. The two-measurement equation is a separate estimate and is not guaranteed to be more accurate outside this range.
