Caffeine dose by body weight
Multiply body weight by a target in mg per kg: 70 kg at 3 mg/kg is 210 mg of caffeine. Use the rate your coach, protocol or clinician set, then compare the total with your coffee, pill or pre-workout label. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Weight
- 70
- Dose per kg
- 3
- Dose mg
- 210 mg
- Weight (kg)
- 70
- Dose mg per kg
- 3
Athletes, coaches, and clinicians often scale caffeine to body mass rather than taking a fixed milligram amount. 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.
Why dose caffeine by milligrams per kilogram
Fixed caffeine pills ignore body size. A one-hundred-milligram capsule is a strong relative dose for a lighter athlete and a mild one for a heavier athlete. Sports nutrition research therefore reports caffeine as milligrams per kilogram of body mass so study arms remain comparable across participants.
Performance protocols for endurance, strength, and team sports frequently cite bands such as three to six mg/kg taken about forty-five to sixty minutes before exercise, while lower rates may suit everyday alertness and higher rates raise the risk of side effects. Using a per-kilogram target does not replace clinical judgment: pregnancy, cardiac conditions, anxiety disorders, sleep debt, and drug interactions can all change what is appropriate. What this tool does is make the arithmetic transparent.
You supply body mass and the rate your coach, lab protocol, or clinician specified; you receive total milligrams you can compare against product labels, pre-workout scoops, or coffee estimates without rewriting the multiply step in every spreadsheet.
Where teams use it and how pricing works
Training plans that prescribe three mg/kg or six mg/kg can post many independent tasks—one per athlete weight—and store the returned milligrams next to the session plan. Supplement label checkers can multiply a stated mg/kg target by self-reported body mass so users see whether a scoop exceeds their protocol. Batch jobs bill each successful computation as one item.
The interactive tool above runs free in the browser for interactive checks. Source inputs and outputs are retained only for the platform retention window and are never used to train models.
What you can do with it
Pre-competition performance protocols
Convert a coach-specified mg/kg rate and each athlete’s body mass into total milligrams for timing caffeine before race or training.
Supplement and label cross-checks
Multiply a user’s target mg/kg by body weight and compare the result to labeled caffeine content of scoops, gels, or drinks.
FAQ
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.
What happens if weight is zero or negative?
Weight must be a finite number strictly greater than zero.
My scale shows pounds. How do I use the calculator?
Divide your weight in pounds by 2.20462 to get kilograms, then enter that figure. The milligrams-per-kilogram target only works with body mass in kilograms.
How long before training is a caffeine dose usually taken?
Performance protocols for endurance, strength and team sports often cite about 45 to 60 minutes before exercise. Follow the timing your coach or protocol gives, because the calculator only works out the amount.
Why scale caffeine to body weight instead of taking a fixed pill?
A fixed pill ignores body size: a 100 mg capsule is a strong dose for a lighter athlete and a mild one for a heavier athlete. That is why sports research reports caffeine in milligrams per kilogram.
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/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
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
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 call the calculator and read the result
Missing or non-numeric fields fail with a clear message naming the field. Convert pounds to kilograms by dividing by 2.20462 before calling if your scale uses imperial units, and convert grams of product to milligrams of pure caffeine using the label concentration rather than assuming every gram of powder equals one milligram of caffeine. Provide weight in kilograms and dose_per_kg in milligrams of caffeine per kilogram of body mass. The service computes dose_mg equals weight_kg times dose_mg_per_kg, rounds the product to six decimal places for stable storage, and returns those fields together with the unit string mg and the formula label. Aliases such as mass, weight_kg, body_weight, mg_per_kg, dose_mg_per_kg, and target_dose are accepted so forms and scripts do not need a single field name. Weight must be strictly greater than zero; zero or negative mass is rejected with invalid_input because a non-positive body mass is not meaningful for dosing. A negative dose_per_kg is also rejected. There is no network lookup, no model inference, and no dependence on the current date—the same inputs always produce the same JSON.
Where teams use it and how pricing works
Use this endpoint when a sports science notebook, team dashboard, research pipeline, or intake form needs a repeatable total caffeine dose without embedding ad-hoc floating-point code in every client. Programmatic calls use the ForHosting KIT prepaid balance at $0.002 per successful request, with no subscription and no charge when validation fails. Because the arithmetic is tiny and fully local to the Worker, latency is dominated by the task queue handshake rather than by computation, which makes the capability suitable for high-frequency form validation as well as offline reprocessing of historical athlete tables.
Integration use cases
Sports science notebooks and dashboards
Store deterministic dose_mg next to weight and protocol rate so cohort exports share one formula definition across labs and seasons.
Technical questions
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).
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.
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.