Estimate calories burned by activity MET, weight and duration
A 72 kg person doing a 6.5 MET activity for 45 minutes burns about 351 kilocalories: MET times weight times hours. Enter the MET value of your own activity and get an estimate you can check. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
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Worked example
- Weight (kg)
- 72
- Met
- 6.5
- Duration minutes
- 45
- Calories burned kcal
- 351
- Duration hours
- 0.75
Estimate the energy used during an activity from three practical inputs: body weight in kilograms, the activity's metabolic equivalent value, and duration in minutes. The calculator applies the standard MET relationship, converting minutes to hours before multiplying intensity by body mass and time. It returns the estimated kilocalories together with normalized inputs and the formula used, making the result easy to inspect or reproduce. This is a deterministic planning estimate for exercise logs, lessons, and software workflows, not a personalized clinical measurement.
Apply the MET formula correctly
A metabolic equivalent of task, usually shortened to MET, describes an activity's energy demand relative to rest. To estimate calories for a session, multiply the activity MET value by body weight in kilograms and by duration in hours. For a seventy-two-kilogram person doing a 6.5 MET activity for forty-five minutes, duration is 0.75 hours and the estimate is 351 kilocalories.
The response includes that total, the converted duration, every normalized input, and a formula label. Those extra fields make the result suitable for audit logs and help catch unit mistakes. Supply kilograms, not pounds, and minutes, not seconds.
If your source records pounds, convert that value before calling this capability. The computation is pure arithmetic: it does not infer an activity, choose a MET value, contact a third party, or adjust its result based on the current date. Results are rounded to six decimal places to prevent distracting floating-point tails while retaining useful precision for short sessions and automated calculations.
Validate inputs and interpret the estimate
Body weight and duration must both be finite numbers greater than zero. The MET field must also be finite and cannot be negative; zero is accepted as a mathematical boundary and returns zero calories, though real recorded activities normally use a positive MET. Validation happens before multiplication, so malformed form submissions and broken data rows are easy to identify.
Remember that a MET calculation is an estimate rather than direct calorimetry. Published MET values describe standardized activity intensities, while an individual's actual expenditure can vary with movement efficiency, terrain, temperature, fitness, body composition, and how accurately the chosen MET describes the effort. Use the number as a consistent comparison or planning value, not as a guarantee of energy balance or weight change.
The output is expressed in nutritional kilocalories, commonly labeled Calories in food and fitness contexts. It represents the formula's total energy estimate for the entered duration. It does not subtract resting expenditure, calculate basal metabolic rate, estimate daily energy needs, or prescribe exercise.
For clinical decisions or recovery planning, combine the result with qualified professional advice and measurements appropriate to the person.
Use the calculator in logs, lessons, and applications
The capability works well wherever a MET value has already been selected and a repeatable calculation is more useful than a black-box prediction. A fitness journal can turn activity rows into comparable calorie estimates. A coach can prepare rough session summaries while keeping the source intensity, weight, and duration visible.
Teachers can demonstrate how intensity, mass, and time affect the result independently: doubling duration doubles the estimate, and changing MET changes it in direct proportion. The browser and server paths share the same deterministic solve function, which keeps interactive checks aligned with automated jobs. For reliable pipelines, preserve the original MET source and units with your own record, validate kilograms before submission, and treat changes in body weight as changes to the calculation input rather than silently reusing an old profile value.
If you only know an activity name, first obtain an appropriate MET from a reputable activity compendium or your own validated mapping. This tool intentionally does not guess intensity from labels such as running or cycling, because pace, resistance, and effort can place the same broad activity in very different MET categories.
What you can do with it
Workout journal estimates
Convert recorded MET, weight, and session duration into consistent kilocalorie estimates for personal or coaching logs.
Exercise science lessons
Demonstrate the direct relationship between activity intensity, body mass, elapsed time, and estimated energy expenditure.
Fitness application pipelines
Calculate auditable values for activity records using deterministic output with explicit normalized inputs and formula details.
FAQ
What formula does this calculator use?
It uses kcal = MET × weight in kilograms × duration in hours. Entered minutes are divided by sixty before multiplication.
What units should I enter?
Enter body weight in kilograms, activity duration in minutes, and MET as a dimensionless activity intensity value.
Is the result a precise measurement?
No. It is a standardized estimate. Actual energy expenditure varies between people and conditions even for the same listed MET.
How many calories does a 72 kg person burn in 45 minutes at 6.5 MET?
About 351 kilocalories. The 45 minutes become 0.75 hours, and 6.5 × 72 × 0.75 gives 351. Change any of the three values to see how the estimate moves.
Does the result subtract the calories I would burn at rest?
No. The figure is the formula's total estimate for the session. It does not subtract resting energy, work out your basal metabolic rate or estimate your daily needs.
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/fitness2/calories-burned-activity-met \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"weight_kg":72,"met":6.5,"duration_minutes":45}'const res = await fetch("https://api.kit.forhosting.com/fitness2/calories-burned-activity-met", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"weight_kg": 72,
"met": 6.5,
"duration_minutes": 45
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/fitness2/calories-burned-activity-met",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"weight_kg": 72,
"met": 6.5,
"duration_minutes": 45
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/fitness2/calories-burned-activity-met", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"weight_kg":72,"met":6.5,"duration_minutes":45}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"weight_kg":72,"met":6.5,"duration_minutes":45}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/fitness2/calories-burned-activity-met", 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_kg": 72,
"met": 6.5,
"duration_minutes": 45
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "fitness2.calories_burned_activity_met",
"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
Apply the MET formula correctly
Because people commonly record exercise in minutes, this calculator first divides duration_minutes by sixty. The complete relationship is kcal = MET × weight_kg × duration_hours. Identical inputs therefore always produce identical JSON output.
Validate inputs and interpret the estimate
A missing, zero, negative, infinite, or non-numeric value is rejected with an invalid_input error instead of returning a misleading total.
Use the calculator in logs, lessons, and applications
Developers can call the API for imported workout records and store the returned formula beside each value for traceability. Each successful API item uses the published base price of $0.002; there is no variable usage component or external service dependency.
Technical questions
What happens when weight or duration is zero?
The request returns invalid_input because weight and duration must be finite numbers greater than zero.
How much does an API request cost?
A successful API item costs $0.002. The calculation uses no network service and has no variable usage charge.