Not every farm has a livestock scale. A measuring tape and a simple formula give a usable estimate of live weight — good enough to follow growth, plan rations and dose medicines.
Schaeffer's formula
The formula most widely used for cattle needs two measurements: heart girth and body length.
Weight (lb) = heart girth (in)² × body length (in) ÷ 300
In metric units the same formula becomes:
Weight (kg) ≈ heart girth (cm)² × body length (cm) ÷ 10,840
The metric divisor comes from converting centimetres to inches (÷ 2.54, three times) and pounds to kilograms (× 0.4536): 2.54³ × 300 ÷ 0.4536 ≈ 10,840.
How to measure
- Stand the animal square on level ground, head up and relaxed.
- Heart girth: pass the tape around the chest just behind the front legs and shoulder blades. Pull it snug, not tight, and read it as the animal breathes out.
- Body length: measure from the point of the shoulder to the pin bone (the point of the rump).
- Take each measurement twice. If they differ, measure a third time and use the closest pair.
Worked example
| Heart girth | 180 cm |
|---|---|
| Body length | 150 cm |
| Calculation | 180² × 150 ÷ 10,840 = 32,400 × 150 ÷ 10,840 |
| Estimated weight | ≈ 448 kg |
Know the limits
- It is an estimate. Breed, body condition, pregnancy and gut fill all move the true weight away from the formula.
- It was developed for cattle. Sheep, goats and other species need their own formulas or a scale.
- Small measuring errors matter: girth is squared, so a few centimetres off the girth changes the result noticeably.
- Check the tape against a scale now and then — at a market or a neighbour's farm — to learn how your animals compare.
For tracking growth, consistency matters more than perfect accuracy: the same person, the same tape and the same technique each time. Read more in how to track average daily gain.
In FarmoraX
Choose Tape when recording a weighing, enter the heart girth and body length in centimetres, and FarmoraX works out the weight with Schaeffer's formula. The method is saved with each weighing, so you can always tell a scale weight from a tape estimate.