Ideal weight calculator
For a man 180 cm tall, ideal body weight comes out at 72.6 kg with Robinson, 71.5 kg with Miller and 75.0 kg with Devine. See all three side by side, or pick one, from just sex and height. Free in your browser.
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Worked example
- Sex
- Male
- Height (cm)
- 180
- Robinson estimate
- 72.6
- Miller estimate
- 71.5
- Devine estimate
- 75
Estimates ideal body weight in kilograms from sex and height using the Robinson, Miller, and Devine formulas, returning each requested formula's result or all three at once.
Three classic formulas from one height
Each formula starts from a base weight at 60 inches, or five feet, and adds a fixed amount for every inch above that. Robinson uses 52 kg plus 1.9 per inch for men and 49 plus 1.7 for women. Miller uses 56.2 plus 1.41 for men and 53.1 plus 1.36 for women. Devine uses 50 plus 2.3 for men and 45.5 plus 2.3 for women. Your height in centimeters is divided by 2.54 to get inches, and the result is given in kilograms.
Reading the results sensibly
Because the formulas share the same per-inch structure but differ in base weight and slope, they rarely agree, and Devine usually reads highest for tall men. Showing all three lets you compare instead of trusting a single point estimate. Heights must be between 152.4 and 250 cm, since the equations are undefined below their 60-inch baseline. Results have one decimal by default, and you can choose whole kilograms or two decimals. The figure is a reference estimate based on sex and height alone.
Three clinical formulas from height and sex
Robinson: 52 + 1.9 per extra inch for men, 49 + 1.7 for women. Miller: 56.2 + 1.41 for men, 53.1 + 1.36 for women. Devine: 50 + 2.3 for men, 45.5 + 2.3 for women.
Results are in kilograms. For a 180 cm male, robinson is 72.6, miller is 71.5, and devine is 75.0 kg.
Rounding, decimals and the minimum height
The decimals parameter defaults to 1 and must be an integer from 0 to 2, letting you return whole kilograms or one or two decimal places. The upper bound is 250 cm. All three formulas share the same per-inch slope structure but differ in their base weight and coefficients, which is why Devine typically reads highest for tall men — returning all three lets a clinician compare rather than trust a single point estimate.
What you can do with it
Dosing references
Give clinicians an IBW estimate that feeds weight-based medication and ventilation calculations.
Fitness onboarding
Show a new user a target-weight range from height without asking for current weight.
FAQ
Which formulas are supported?
Robinson, Miller, and Devine; request one or return all three at once with 'all'.
What units are the results in?
Kilograms, rounded per the decimals parameter (default 1).
Why can the three formulas disagree?
They share a per-inch structure but use different base weights and slopes, so results differ, especially for tall people.
Why is there a minimum height of 152.4 cm?
All three formulas start at 60 inches, or five feet, which is exactly 152.4 cm, and add a set amount for each inch above it. Below that baseline the equations are not defined, so shorter heights are rejected.
Where is ideal body weight used?
Clinicians use it as a reference for weight-based medication doses and ventilation settings, and fitness apps use it to suggest a target range from height alone, without asking for current weight.
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/dev/ideal-weight \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"sex":"male","height_cm":180}'const res = await fetch("https://api.kit.forhosting.com/dev/ideal-weight", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"sex": "male",
"height_cm": 180
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/dev/ideal-weight",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"sex": "male",
"height_cm": 180
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/dev/ideal-weight", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"sex":"male","height_cm":180}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"sex":"male","height_cm":180}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/dev/ideal-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
{
"sex": "male",
"height_cm": 180
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "dev.ideal_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.
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
Three clinical formulas from height and sex
The calculator estimates ideal body weight from two required inputs — sex ('male' or 'female') and height_cm — using three classic clinical formulas. Height is converted to inches (height_cm / 2.54) and the inches above 60 (five feet) drive each equation. The formula parameter selects one of 'robinson', 'miller', 'devine', or 'all' (the default); unrequested formulas are returned as null so the response shape stays constant.
Rounding, decimals and the minimum height
Because every formula is anchored at 60 inches, the tool enforces a minimum height: height_cm must be at least 152.4 cm (exactly 60 inches), and a shorter value throws 'altura mínima 152.4 cm' since the equations are undefined below their baseline.
Validation and typed errors
The top-level input must be a plain object — arrays and null are rejected. Validation precedes any arithmetic. sex must be exactly 'male' or 'female'; any other value throws the typed invalid_input error 'sex inválido'. height_cm must be a finite number within 152.4 to 250, so a string, NaN, or an out-of-range figure fails immediately. decimals outside 0-2 throws 'decimals fuera de rango', and an unrecognised formula throws 'formula inválida'. Failed API tasks are never charged, so you can probe boundary heights or an invalid sex value against the live endpoint without spending prepaid balance.
Integration use cases
EHR integration
Batch patient heights through the API to populate IBW fields with a chosen formula.
Technical questions
Why is there a minimum height?
The formulas are anchored at 60 inches, so height_cm must be at least 152.4 cm.
Is it free?
Yes in the browser widget; the API runs the same core from $0.002 per call.