Most horse owners never get near a livestock scale, but you still need a number. Agriculture Victoria explains that weight estimation is needed for working out feed requirements and for "determining the correct dosage of worm treatments and other drugs" [1]. Guess too low and you under-dose a wormer; guess too high and you over-feed an easy keeper.
The good news: a soft tape measure, a helper and five minutes gets you a useful estimate. Here are the three methods Agriculture Victoria publishes, how to use each one, and how far to trust them.
A note on medications. Every method here is an estimate. For any medication where the dose matters, check the weight and dose with your vet.
Method 1: The girth-and-length formula (most useful)
Agriculture Victoria gives this formula [1]:
Weight (kg) = girth (cm) × girth (cm) × length (cm) ÷ 12,000
It's based on Carroll and Huntington's 1988 study in the Equine Veterinary Journal [1].
How to measure
- Stand the horse square on firm, level ground, relaxed, with weight on all four feet. Agriculture Victoria says the same for height measurements [1].
- Girth: run the tape right around the barrel, just behind the elbow and over the lowest point of the withers, where a girth or surcingle sits. Pull it snug but not tight, and read it as the horse breathes out.
- Length: measure in a straight line from the point of the shoulder to the point of the buttock. Agriculture Victoria's page shows the measuring points in a figure (Figure 5) [1].
- Measure each twice and use the average.
Worked example
A horse with a girth of 190 cm and a length of 160 cm:
190 × 190 × 160 ÷ 12,000 = 481 kg (481.3 to one decimal place)
Our horse weight calculator does this sum for you, and converts inches if your tape only reads in imperial (1 inch = 2.54 cm).
Method 2: Height and condition score table
If you know your horse's height in hands and can condition score it, Agriculture Victoria publishes this table [1]:
| Condition score | 12 hh | 13 hh | 14 hh | 15 hh | 16 hh |
|---|---|---|---|---|---|
| 1 (poor) | 190 | 240 | 310 | 390 | 420 |
| 2 (moderate) | 210 | 285 | 330 | 420 | 470 |
| 3 (good) | 250 | 345 | 395 | 460 | 505 |
| 4 (fat) | 300 | 370 | 460 | 535 | 570 |
| 5 (very fat) | 360 | 460 | 540 | 610 | 670 |
Weights in kg. 1 hand = 10.2 cm (4 inches). [1]
So a 15 hh horse in good condition (score 3) is estimated at 460 kg [1]. The table stops at 12 and 16 hands, so don't stretch it to minis or big warmbloods.
Measuring height: stand the horse on level ground, relaxed and square, and measure to the highest point of the withers, allowing for shoes [1].
Method 3: The weight tape
Weight tapes sold at saddleries go around the girth and read off an estimated weight. Agriculture Victoria mentions them as an alternative to its table [2]. They're quick and handy for tracking change, but they only use one measurement, so the girth-and-length formula takes more of the horse's shape into account. Whatever you use, use the same method each time so the trend is meaningful.
How to condition score (you'll need it anyway)
Agriculture Victoria calls body condition "the most reliable indicator of the suitability of a horse's diet" [1]. Its 0–5 system scores the neck, back and ribs, and pelvis/rump, using half scores where needed. Use the pelvis and rump as the base, then adjust by half a point if the neck or ribs differ by a full point or more [1].
A quick guide from the page [1]:
- 0 very poor: skin tight over bones, very prominent backbone and pelvis, marked ewe neck
- 1 poor: ribs easily visible, sunken rump
- 2 moderate: ribs just visible, flat rump either side of the backbone, narrow but firm neck
- 3 good: ribs just covered but easily felt, rounded rump, no crest
- 4 fat: gutter along the back, ribs and pelvis hard to feel, slight crest
- 5 very fat: ribs buried, deep gutter, marked crest, folds of fat.
Agriculture Victoria warns that letting condition fall below 2 is likely to compromise a horse's welfare [1], and its basic care page says the same: you should be able to feel, but not see, the ribs [3]. In winter, a heavy coat hides a lot, so run your hands over the horse rather than relying on your eyes [1].
Poor condition isn't always about feed; it can come from worms, bad teeth, injury or illness [1].
How accurate are these methods?
Agriculture Victoria is honest about it: accurate weight estimation "is an art that requires a lot of experience" [1]. Expect the methods to be least reliable for:
- foals and young horses, whose proportions differ
- pregnant mares
- very fit or very fat horses
- ponies and minis outside the table's 12–16 hh range.
If you need a precise number (for anaesthetic, or a horse on long-term medication), ask your vet. Some practices, studs and racing stables have scales.
Put the number to work
Feed. Agriculture Victoria's basic guide is roughly 1–2 kg of roughage per 100 kg of bodyweight a day [3]. For feed budgets it suggests using 1.7% of bodyweight as the safe daily intake of dry feed. For a 500 kg horse that's 500 × 1.7 ÷ 100 = 8.5 kg [2]. It also advises that at least 70% of the ration should be roughage [2]. The feed calculator runs these numbers for you.
Weight gain. If your horse needs to put on condition, Agriculture Victoria advises increasing feed by no more than 10% at a time, and says visible weight gain can take several months [2].
Worming. Dose to your estimate and round up to the next mark on the syringe, as your vet advises.
Compare the two methods on the same horse
Try both methods and see how close they come. Take a 15 hh horse you'd score as a 3 ("good"). The table estimates 460 kg [1]. If the same horse has a girth of 185 cm and a length of 162 cm, the formula gives 185 × 185 × 162 ÷ 12,000 = 462 kg. When the two methods agree that closely, you can be fairly confident in the number. If they're 50 kg or more apart, re-measure, re-score, and ask your vet if the number matters for a medication.
Frequently asked questions
Can I use inches? Yes. Multiply inches by 2.54 to get centimetres before using the formula, or let the weight calculator convert for you.
Does it work for ponies and foals? Less reliably. The table only covers 12–16 hands [1], and foals have different proportions. Check doses with your vet.
How often should I weigh my horse? Monthly is a good routine, and more often if you're changing feed, managing a laminitis-prone horse or trying to put weight on.
Is a weight tape good enough for worming? It's a reasonable start, but if you're unsure, ask your vet. Under-dosing helps worms become resistant.
Make it a habit
Weigh and condition score once a month, and more often in spring if you have an easy keeper at risk of laminitis. Write the numbers in your horse's health record. A 20–30 kg change you've measured is much easier to spot and act on than one you've only half-noticed.
