ForHosting KIT · Developer Utilities

Estimate body frame size from height and wrist measurement

This body frame size estimator uses two simple measurements—standing height and wrist circumference—to place a result in a small, medium, or large reference category.

● BetaFree · in your browser

Run — free How it works & API

Use it from WebAPIEmailTelegramApp soon

It divides height in centimetres by wrist circumference in centimetres and compares that ratio with a fixed table. The calculation is deterministic, transparent, and easy to reproduce. It is intended as a general sizing reference, not as a diagnosis or a measurement of body fat, muscle mass, health, or ideal weight. Enter both values as positive numbers in the same unit scale; the form and API describe centimetres so results remain consistent.

How to use it

Enter your values in the form above. The tool checks them before calculating and shows the result on the same page.

Check your inputs

Use the labels and units shown next to each field. If something is missing or outside the allowed range, the page points to the field to fix.

Use it again or automate it

Use the browser tool for individual checks and the API when you need the same capability in an automated workflow.

What you can do with it

Get an answer now

Enter one set of values and see the result without building a spreadsheet or script.

Compare scenarios

Change one value at a time and rerun the calculation to understand what affects the result.

Automate repeated work

Use the API when the same calculation needs to run inside your product or workflow.

FAQ

How is body frame size estimated?

Height is divided by wrist circumference, then the resulting ratio is compared with the small, medium, and large reference bands.

What are the category boundaries?

A ratio above 10.4 is small, 9.6 through 10.4 inclusive is medium, and below 9.6 is large.

Which units should I enter?

Enter both height and wrist circumference in centimetres. Mixing unit systems makes the ratio invalid for this table.

What happens if a measurement is zero or negative?

The request fails with invalid_input because both height and wrist circumference must be positive finite numbers.

Is this a medical assessment?

No. It is a general ratio-based frame estimate and does not measure body composition, bone density, or health.

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

POSThttps://api.kit.forhosting.com/calc3/body-frame-size-estimate

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/calc3/body-frame-size-estimate \
  -H "Authorization: Bearer $KIT_KEY" \
  -H "Content-Type: application/json" \
  -d '{"height":175,"wrist":17.5}'

const res = await fetch("https://api.kit.forhosting.com/calc3/body-frame-size-estimate", {
  method: "POST",
  headers: {
    "Authorization": `Bearer ${process.env.KIT_KEY}`,
    "Content-Type": "application/json"
  },
  body: JSON.stringify({
    "height": 175,
    "wrist": 17.5
  })
});
const { task_id } = await res.json();

import os, requests

res = requests.post(
    "https://api.kit.forhosting.com/calc3/body-frame-size-estimate",
    headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
    json={
    "height": 175,
    "wrist": 17.5
},
)
task_id = res.json()["task_id"]

<?php
$res = file_get_contents("https://api.kit.forhosting.com/calc3/body-frame-size-estimate", false, stream_context_create([
  "http" => [
    "method"  => "POST",
    "header"  => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
    "content" => '{"height":175,"wrist":17.5}',
  ],
]));
$task = json_decode($res, true);

body := bytes.NewBufferString(`{"height":175,"wrist":17.5}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/calc3/body-frame-size-estimate", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)

Example request

{
  "height": 175,
  "wrist": 17.5
}

Example response

{
  "task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
  "type": "calc3.body_frame_size_estimate",
  "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

Per request$0.002

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.

Read the full KIT documentation →