Horse weight calculator
Get the weight your ration, dewormer dose and trailer limit depend on without a walk-on scale: a 72 in heart girth and 68 in body length give 1068.2182 lb, or 484.5356 kg. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Heart girth
- 72 in
- Body length
- 68
- Girth in
- 72 in
- Length in
- 68
- Weight lb
- 1,068.2182
- Weight (kg)
- 484.5356
A horse's body weight is the figure every ration, dewormer dose, and trailer limit depends on, yet few barns keep a walk-on scale. The practical field method is the heart-girth formula used by equine weight tapes: square the heart girth in inches, multiply by body length in inches, and divide by three hundred and thirty to estimate pounds, then convert to kilograms with the international avoirdupois pound.
What the heart-girth formula estimates and how pounds become kilograms
The field method for estimating a horse's live mass without a walk-on scale is the heart-girth identity used by equine weight tapes and by the Carroll and Huntington formula those tapes implement. Convert both measurements to inches if they were taken in centimetres by dividing each by 2.54, the exact international inch.
A typical riding horse with a seventy-two inch girth and a sixty-eight inch length therefore lands near one thousand and sixty-eight pounds, about four hundred and eighty-five kilograms, which is the order of magnitude a barn tape would quote before you still confirm body-condition score with a veterinarian.
The divisor 330 is the adult-horse constant published for mature horses; this calculator does not switch to yearling or pony divisors, does not apply a body-condition hair-coat adjustment, and does not replace a certified scale when a milligram-per-kilogram drug dose or a legal trailer plate depends on a weighed mass. Zero and negative measurements are not a horse: they fail rather than invent a live weight.
Where a horse weight calculator earns its keep
Barns that worm, vaccinate, or balance a winter hay ration use a horse weight calculator so the first pass at milligrams per kilogram is not a guess copied from last year's hunter. Rescue intake desks and clinic front desks batch girth and length from the card and need a deterministic oracle that rejects a zero-inch paste instead of silently publishing a zero-pound horse.
Trailer and shipper checklists compare the estimate against plate limits before a pair of drafts is loaded; the figure is orientation, not a certified weighbridge, and the page says so. Failed validation does not consume balance. Keep both measurements honest, pin pounds and kilograms in tests, and you get a reproducible live-weight estimate for homework, LMS plugins, barn spreadsheets, and feeding apps.
Related searches for a dog food scoop, a cat calorie target, a human BMI, or a feed-conversion ratio are different intents: stay on this page when the question is only the horse's estimated body weight implied by heart girth and body length. This estimate is educational and does not replace a veterinarian or a scale, especially for pregnant, emaciated, or clinically ill horses whose shape sits outside the adult tape assumptions.
What you can do with it
Clinic and rescue intake cards
Front desks batch girth and length from the card and get a deterministic live-weight estimate that rejects a zero-inch paste rather than inventing a zero-pound horse.
Centimetre tapes and mixed-unit barns
Send unit cm with both measurements in centimetres when the only tape in the aisle is metric; the same 330 identity and 2.54 conversion produce matching kilograms.
FAQ
Where do I place the tape for heart girth and body length?
Heart girth is the barrel circumference just behind the withers and elbows. Body length runs from the point of the shoulder to the point of the buttock along the side, with the horse standing square.
What if a measurement is zero, negative, or missing?
Every measurement must be a finite positive number; missing fields, empty strings, and non-numeric values are rejected the same way and are not billed.
Does the calculator use a different divisor for ponies or yearlings?
No. It applies the adult-horse constant 330 only.
How do I estimate a horse's weight with a tape measure?
Square the heart girth in inches, multiply by the body length in inches and divide by 330 to get pounds. Pounds are then converted to kilograms at 0.45359237 kg per pound.
Can I enter my measurements in centimetres?
Yes. Each measurement in centimetres is divided by 2.54, the exact inch, before the formula runs, so you get the same estimate as with a tape marked in inches.
Related tools
For developers — API access
Everything on this page is available programmatically. This section is for teams who want to wire it into their own systems; everyone else can just use the tool above.
API endpoint
Prefer to automate it? One authenticated POST creates the task; the result comes back by webhook or a signed link. The same capability also runs here on the web, by email and from Telegram — and soon from our app too.
Call it from your stack
curl -X POST https://api.kit.forhosting.com/bio/horse-weight \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"heart_girth":72,"body_length":68}'const res = await fetch("https://api.kit.forhosting.com/bio/horse-weight", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"heart_girth": 72,
"body_length": 68
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/bio/horse-weight",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"heart_girth": 72,
"body_length": 68
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/bio/horse-weight", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"heart_girth":72,"body_length":68}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"heart_girth":72,"body_length":68}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/bio/horse-weight", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"heart_girth": 72,
"body_length": 68
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "bio.horse_weight",
"status": "queued",
"_links": {
"result": "/tasks/tsk_…/result"
}
}The API is asynchronous: the call returns a task_id immediately and the result arrives by webhook. Polling is capped at 1 req/s per task.
Pricing
Published price — no tokens, no invented credits. A failed task is never charged.
Limits
max_heart_girth | 500 |
max_body_length | 500 |
Errors
| HTTP | Code | Meaning |
|---|---|---|
401 | unauthorized | Missing or invalid API key. |
402 | insufficient_balance | Your balance doesn't cover the task price. |
404 | unknown_type | That task type doesn't exist. |
429 | rate_limited | Too many requests. Use the webhook instead of polling. |
Technical notes
This horse weight calculator accepts heart_girth and body_length as finite positive numbers, an optional unit of in or cm, and returns weight_lb and weight_kg from that identity. Missing, zero, or negative measurements fail with invalid_input instead of inventing a mass.
What the heart-girth formula estimates and how pounds become kilograms
Measure heart_girth as the circumference of the barrel in a vertical plane just behind the withers and the elbows, with the tape snug against the coat and the horse standing square on level ground. Measure body_length from the point of the shoulder, the palpable prominence of the humerus, to the point of the buttock, the tuber ischii, along the side of the body rather than over the spine. Square the heart girth in inches, multiply by the body length in inches, and divide by 330: that quotient is weight_lb, the estimated live weight in pounds. Multiply weight_lb by 0.45359237, the exact international avoirdupois kilogram per pound, to obtain weight_kg.
Input contract, response shape, and error behaviour
Omit unit and the calculator treats both measurements as inches. Example: the same horse measured in centimetres sends unit cm and the two centimetre readings; the kilograms match the inch path because there is one formula, not a second approximate metric divisor. POST a JSON body with two required finite positive numbers and an optional unit. heart_girth is the barrel circumference (aliases girth, heartgirth, hg) and must sit in the open-closed interval from just above zero through five hundred; a miniature's forty-inch girth is legal, a zero or negative paste is not. body_length is the shoulder-to-buttock length (aliases length, bodylength, bl) in the same unit, also a finite positive number no greater than five hundred. unit is a closed pair: in for inches, the native unit of the three-hundred-and-thirty formula, or cm for centimetres, which are converted to inches by dividing by 2.54 before the square-and-product step. Each numeric field may arrive as a JSON number or as a numeric string. Missing fields, empty strings, non-finite values, zero, negatives, values above the declared maxima, and a unit other than in or cm fail with invalid_input naming the field. Those failures are not billed. On success the body echoes the cleaned heart_girth, body_length, and unit, publishes girth_in and length_in as the working inches, and returns weight_lb and weight_kg rounded to four decimal places for stable goldens across runtimes. formula restates the adult identity so a notebook can print the substitution next to the answer. Example: heart_girth 72, body_length 68, unit in is a medium riding horse. Pair the estimate with the body-condition score you already use; this endpoint does not score fat cover or split a ration.
Where a horse weight calculator earns its keep
Exam-prep generators and equine-science katas pin a known seventy-two by sixty-eight inch adult, a centimetre pair, and the invalid_input path for a non-positive girth so a buggy grader cannot accept a negative mass.
Integration use cases
Barn worming and ration checks
Measure heart girth behind the withers and body length from shoulder to buttock, then read weight_lb and weight_kg before the next dewormer or hay ration instead of guessing from last year's hunter.
Technical questions
How do I estimate a horse's weight from girth and length?
Send finite positive numbers for heart_girth and body_length, plus unit in or cm (default in). The API converts to inches if needed, then returns weight_lb = (girth_in² × length_in) / 330 and weight_kg = weight_lb × 0.45359237.
What does the horse weight calculator cost?
The browser tool is free. API requests use prepaid KIT balance at $0.002 per successful call; invalid input is not billed.