ForHosting KIT · Developer Utilities

Caffeine dose by body weight

Athletes, coaches, and clinicians often scale caffeine to body mass rather than taking a fixed milligram amount.

● BetaFree · in your browser

Use it from WebAPIEmailTelegramApp soon

A common performance band is roughly three to six milligrams of caffeine per kilogram of body weight, timed before training or competition, but the right rate depends on protocol, tolerance, and medical advice. This calculator multiplies body weight in kilograms by your chosen milligrams-per-kilogram target and returns a single deterministic total dose in milligrams. The free browser tool and the API share the same arithmetic library, so the number you see on the page matches what a task would return—no network lookup, no randomness, and no dependence on the current date.

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 formula does this calculator use?

Total caffeine in milligrams equals body mass in kilograms multiplied by the target dose in milligrams per kilogram (weight_kg × dose_mg_per_kg).

What is a typical performance caffeine dose per kilogram?

Many sports nutrition protocols cite roughly three to six mg/kg before exercise, but the right rate depends on tolerance, event, and medical advice—this tool only multiplies the rate you choose.

Which units should I use for weight and dose_per_kg?

Use kilograms for weight and milligrams of caffeine per kilogram for dose_per_kg. Convert pounds by dividing by 2.20462 before calling.

What happens if weight is zero or negative?

The request fails with invalid_input and is not charged. Weight must be a finite number strictly greater than zero.

Is the caffeine dose calculator free?

The browser tool is free. API calls cost $0.002 per successful request from your prepaid KIT balance; failed validation is never charged.

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/caffeine-per-kg

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/caffeine-per-kg \
  -H "Authorization: Bearer $KIT_KEY" \
  -H "Content-Type: application/json" \
  -d '{"weight":70,"dose_per_kg":3}'

const res = await fetch("https://api.kit.forhosting.com/health/caffeine-per-kg", {
  method: "POST",
  headers: {
    "Authorization": `Bearer ${process.env.KIT_KEY}`,
    "Content-Type": "application/json"
  },
  body: JSON.stringify({
    "weight": 70,
    "dose_per_kg": 3
  })
});
const { task_id } = await res.json();

import os, requests

res = requests.post(
    "https://api.kit.forhosting.com/health/caffeine-per-kg",
    headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
    json={
    "weight": 70,
    "dose_per_kg": 3
},
)
task_id = res.json()["task_id"]

<?php
$res = file_get_contents("https://api.kit.forhosting.com/health/caffeine-per-kg", false, stream_context_create([
  "http" => [
    "method"  => "POST",
    "header"  => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
    "content" => '{"weight":70,"dose_per_kg":3}',
  ],
]));
$task = json_decode($res, true);

body := bytes.NewBufferString(`{"weight":70,"dose_per_kg":3}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/health/caffeine-per-kg", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)

Example request

{
  "weight": 70,
  "dose_per_kg": 3
}

Example response

{
  "task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
  "type": "health.caffeine_per_kg",
  "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 →