Livestock Weight Estimator
Estimate livestock weight from body measurements without a scale.
Calculate cattle, horse, and pig weight from heart girth and body length using standard livestock weight formulas.
Why Estimate Weight Without a Scale? Large livestock scales are expensive and not always available. Veterinarians, farmers, and ranchers use body measurement formulas to estimate weight for drug dosing, feed planning, market value, and breeding records. These formulas are approximate — accuracy is typically ±10–15%.
Cattle Weight Formula (Schaeffer’s Formula) The most widely used livestock weight formula for cattle (United States, widely adopted): Weight (lb) = (Heart Girth² × Body Length) / 300 Heart Girth: measured in inches, around the body just behind the front legs. Body Length: measured in inches, from point of shoulder to point of pin bone (tuber ischii). This formula was developed by agricultural researchers at US land-grant universities in the early 20th century.
Horse Weight Formula Weight (lb) = (Heart Girth² × Body Length) / 330 Adapted version of the cattle formula with a different constant for horse body proportions. For ponies (under 14.2 hands): use a slightly different constant (300 instead of 330). Alternative: Weight (kg) = (Heart Girth in cm)² × Body Length (cm) / 11,880 × 1.486
Pig Weight Formula Swine estimation is based on heart girth alone (pigs are proportionally shorter): Weight (lb) = (Heart Girth in inches)³ / 400 For metric: Weight (kg) ≈ (Heart Girth in cm / 2.54)³ / 400 × 0.4536 This gives good accuracy for market hogs (~100–250 lb range).
Sheep and Goat Weight Weight (lb) ≈ (Heart Girth − 22) × 3 This simple linear formula works for adult sheep and goats. More accurate specialized formulas exist for specific breeds.
Tips for Accurate Measurement Animal must be standing squarely on level ground. Heart girth tape: hold snugly but not tight; measure natural breathing position. Use a flexible measuring tape or a purpose-made “weigh tape” (marked in weight equivalents). Weigh tapes pre-calculate the formula and display weight directly — sold at farm stores. Average 2–3 measurements for better accuracy. Accuracy decreases for very thin (body condition score 1–2) or very fat (BCS 5) animals.
Body Condition Scoring (BCS) BCS (1–5 scale for cattle) or (1–9 scale for horses) assesses fat coverage. BCS affects the accuracy of measurement-based weight formulas. Very thin animals have lower actual weight than formula predicts. Very fat animals have higher actual weight.