ForHosting KIT · Developer Utilities

Maximum heart rate calculator

This maximum heart rate calculator estimates how high your heart rate in beats per minute is expected to climb during all-out effort, using only your age.

● BetaFree · in your browser

Run — free How it works & API

Use it from WebAPIEmailTelegramApp soon

It applies three well-known population formulas side by side: the classic Fox rule of thumb two hundred twenty minus age, the Tanaka regression two hundred eight minus zero point seven times age, and the Gulati equation two hundred six minus zero point eight eight times age. Seeing all three at once helps you compare a simple classroom rule against research-based alternatives without running a lab stress test. The engine is fully deterministic: the same age always yields the same rounded bpm values, with no network calls, no sampling, and no date-dependent shortcuts. Use it free in the browser when planning zones, teaching fitness math, or checking homework, or call the API at $0.002 per successful request when you need reproducible HRmax fixtures in coaching software, CI tests, or education tools.

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

What does the maximum heart rate calculator cost?

It is free in your browser on this page. Through the API a successful request costs $0.002; invalid inputs are not charged.

Which formulas are used?

Fox: HRmax = 220 − age. Tanaka: HRmax = 208 − 0.7 × age. Gulati: HRmax = 206 − 0.88 × age. The response also includes the mean, min, and max of those three estimates.

What happens if age is zero or negative?

The input is rejected with invalid_input. Age must be a positive finite number; non-positive values are not valid for these maximum heart rate formulas.

Is this a medical measurement of my true max heart rate?

No. These are population regression estimates from age alone. True individual maximums vary; use clinical or supervised testing when precision matters for health decisions.

Why are results rounded to a precision?

Floating-point products need a stable display width for goldens and JSON. Default precision is 2 decimal places; you can set precision from 0 to 15.

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/health/max-heart-rate

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/health/max-heart-rate \
  -H "Authorization: Bearer $KIT_KEY" \
  -H "Content-Type: application/json" \
  -d '{"age":40}'

const res = await fetch("https://api.kit.forhosting.com/health/max-heart-rate", {
  method: "POST",
  headers: {
    "Authorization": `Bearer ${process.env.KIT_KEY}`,
    "Content-Type": "application/json"
  },
  body: JSON.stringify({
    "age": 40
  })
});
const { task_id } = await res.json();

import os, requests

res = requests.post(
    "https://api.kit.forhosting.com/health/max-heart-rate",
    headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
    json={
    "age": 40
},
)
task_id = res.json()["task_id"]

<?php
$res = file_get_contents("https://api.kit.forhosting.com/health/max-heart-rate", false, stream_context_create([
  "http" => [
    "method"  => "POST",
    "header"  => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
    "content" => '{"age":40}',
  ],
]));
$task = json_decode($res, true);

body := bytes.NewBufferString(`{"age":40}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/health/max-heart-rate", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)

Example request

{
  "age": 40
}

Example response

{
  "task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
  "type": "health.max_heart_rate",
  "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.

Limits

`max_age`	120
`min_age`	1e-9

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 →

Run — free