Pig Weight Estimator
Worked Examples
A crossbreed finisher and a native pig, measured the same way and answered by different formulas — because one formula on both is how a native pig gets overpriced by a fifth.
The formulas, and who fitted them
Every number this tool produces comes from one of three published regressions. None of them is ours, all of them have a range they were fitted on, and the range is part of the formula — using one outside it is extrapolation whatever the calculator prints.
| Formula | Fitted on | R² | Band |
|---|---|---|---|
| Heart girth only (improved breeds) | 100 growing-finishing pigs, 50 to 273 lb (23 to 124 kg) | 0.98 | ±4.5 kg |
| Heart girth and body length (improved breeds) | Finishing pigs, roughly 150 to 300 lb (68 to 136 kg) | 0.95 | ±4 kg |
| Philippine native pig (girth and length) | 54 Philippine native pigs, 20 to 50 kg | 0.92 | ±3 kg |
Example 1 of 2
A crossbreed finisher, ready to sell
Landrace × Large White, looking about ready. Heart girth 117 cm, body length 130 cm, and a buyer offering ₱190/kg liveweight.
| Input | Value |
|---|---|
| Heart girth | 117 cm (behind the front legs) |
| Body length | 130 cm (ears to tail base) |
| Breed type | Improved / crossbreed |
| Price offered | ₱190/kg liveweight |
| Result | Value | Notes |
|---|---|---|
| Estimate | 119.2 kg | Heart girth only (improved breeds) |
| Realistic range | 114.7 – 123.7 kg | The published ±4.5 kg band. |
| Cross-check | 123.6 kg | Second formula, shown separately and never averaged in. |
| What that is worth | ₱21,793 – ₱23,503 | A ₱1,710 spread on one pig. |
That last row is the whole point of the tool. The two formulas agree closely — 119.2 and 123.6 kg — so this is a good measurement. But even a good measurement carries ₱1,710 of uncertainty at ₱190/kg. Enough to decide it is time to sell. Not enough to argue with a buyer about two kilos.
How to use this on your farm
Measure three times and take the average. A 2 cm error on the girth is 3 to 4 kg on the weight, which at ₱190/kg is ₱600 to ₱760 — more than the whole day's labour. Measure while she is eating; a pig that is standing still is a pig you can measure twice.One number worth seeing: divide by 10,840 instead of 14,400 — a divisor that circulates in Filipino farming groups — and these same two tape readings give 164.2 kg. That is 38% heavier than the pig is, or about ₱8,550 of pig that does not exist. People price on that and find out at the buyer's scale.
Example 2 of 2
A Philippine native pig — and why it gets its own formula
The black biik you see in yards across the Visayas and Mindanao. Heart girth 70 cm, body length 60 cm. Native pork sells at a premium, often ₱250 to ₱300/kg liveweight, so getting the weight right matters more per kilo than it does on a crossbreed.
| Input | Value |
|---|---|
| Heart girth | 70 cm |
| Body length | 60 cm |
| Breed type | Philippine native |
| Price offered | ₱260/kg liveweight |
| Result | Value | Notes |
|---|---|---|
| Estimate | 28 kg | Philippine native pig (girth and length) |
| Realistic range | 25 – 31 kg | Derived from the study's R² of 0.92. |
| What that is worth | ₱6,500 – ₱8,060 | At ₱260/kg. |
| Cross-check | None offered | The two-tape formula is an improved-breed formula. Running it here would reintroduce the error. |
Here is the number that justifies a separate formula. Put this same 70 cm girth through the improved-breed girth-only model — the one the calculator refuses to run on a native pig — and it says 33.8 kg, which is 21% heavier than the Philippine study says. At ₱ 260/kg that is ₱1,512 of pig that is not there, on an animal weighing under thirty kilos.
The two-tape formula misses in the other direction here — 20.4 kg, well below the native figure — which is its own reason not to show it: at this size it is outside the 68 to 136 kg finishing range it was fitted on, and a cross-check that is extrapolating is not a check. Two Western formulas, one too high and one too low, and neither of them was fitted on a single native pig.
The native formula comes from Paras & Cu-Cordoves, "Estimating liveweight of Philippine native pigs using external body measurements", Philippine Journal of Veterinary and Animal Sciences 40(1), 2014. Fifty-four animals, 20 to 50 kg. That is a small study and it is the only published Philippine one — which is exactly why the calculator refuses to run a native pig through the Western girth-only formula rather than quietly substituting it when you leave the length blank.
Bisaya / Cebuano
Ang native nga baboy lahi og porma. Mas mubo, mas lig-on ang lawas. Kung gamiton nimo ang pormula para sa Landrace o Large White, mogawas nga mas bug-at siya kaysa sa tinuod, mga 15 ngadto sa 20 porsiyento.
Kinahanglan gyud ang duha ka sukod para sa native: ang libot sa dughan ug ang gitas-on sa lawas. Kung ang gitas-on ra ang wala nimo, ayaw na lang gamita ang pormula. Mas maayo pa nga walay numero kaysa sa numero nga sayop.
When to stop using a tape
Under about 20 kg, none of these formulas were fitted and all of them misbehave — the girth-only line actually crosses zero around 51 cm of girth, which is why the calculator refuses rather than printing a negative weight. A ₱200 hanging scale from any hardware store beats every formula here on a piglet.
And if you are selling by the kilo on a regular basis, buy a real scale. The tape is for deciding when to sell, working out a feed ration, and checking that a buyer's number is in the right neighbourhood. It is not for settling the sale, and a page that told you otherwise would be doing you harm.
The long version of all of this — where exactly to put the tape, a girth lookup table, and the five mistakes that cost the most — is in how to estimate pig weight without a scale .