EPOC afterburn estimate calculator
Estimates the extra calories your body burns after a workout ends: 80% intensity for 45 minutes at 70 kg gives about 105 kcal of afterburn. Every factor is shown, so you can check the arithmetic yourself. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Intensity
- 80
- Duration
- 45
- Weight
- 70
- Epoc kcal
- 105 kcal
- Epoc kj
- 439.32
- Intensity percent
- 80
- Intensity fraction
- 0.8
Excess post-exercise oxygen consumption, often called EPOC or the afterburn effect, is the elevated energy cost that continues after a workout ends while the body restores oxygen debt, clears metabolites, and returns to resting homeostasis. Coaches, athletes, and app builders need a transparent number for that tail, not a black-box AI guess that drifts between model versions. This EPOC afterburn estimate calculator takes relative workout intensity, session duration, and body weight, applies a fixed linear model, and returns kilocalories of estimated excess burn plus the intermediate fractions and rates you can audit.
How the linear EPOC afterburn model works
Start with relative intensity as a fraction of maximal effort. You may send intensity as a percent from just above zero through one hundred, or as a fraction in the open-closed interval from zero exclusive through one inclusive; a value of zero point eight means eighty percent effort, and a value of eighty means the same eighty percent when interpreted as a percent. Duration is the bout length in minutes, converted to hours by dividing by sixty.
Body weight is mass in kilograms so the estimate returns absolute kilocalories rather than a unitless index. The linear planning formula multiplies a fixed coefficient K of two point five kilocalories per kilogram per hour at full intensity by the intensity fraction, by duration in hours, and by weight. Example: eighty percent intensity, forty-five minutes, and seventy kilograms yields two point five times zero point eight times zero point seven five times seventy, which is one hundred five kilocalories of estimated afterburn.
The pipeline is deterministic floating-point arithmetic with no random seeds, no wall-clock timestamps, no network calls, and no model drift. Entries must be finite; NaN and Infinity are rejected.
Where EPOC afterburn calculators show up in real work
Personal trainers and strength coaches estimate afterburn when explaining why a short hard interval session can still matter on the weekly energy ledger even after the clock stops. Endurance athletes and HIIT clubs compare recovery cost across intensity targets when planning back-to-back hard days. Physical education teachers and sports science labs assign homework that multiplies intensity fraction by hours and mass so students see duration and effort as separate levers on excess oxygen debt.
Nutrition coaches combining food logs with training estimates want a transparent afterburn number rather than a marketing claim of hundreds of free calories. Treat session calories burned from MET tables, TDEE with activity multipliers, VO2-based energy equations, and named-activity directories as separate product intents rather than overloading this EPOC afterburn estimate calculator page with every related health formula. Keep requests small, pin the rounded outputs in tests, and you get reproducible afterburn figures for coaching dashboards, LMS plugins, and edge workers without standing up metabolic cart infrastructure of your own.
What you can do with it
Coaching afterburn estimates
Turn relative intensity, session minutes, and client body weight into a consistent EPOC kilocalorie figure for training diaries and weekly energy reviews.
Classroom energy-balance drills
Generate answer keys for exercise-science homework that multiplies intensity fraction by hours and kilograms without spreadsheet drift.
FAQ
How is EPOC afterburn calculated?
Intensity may be percent (0–100] or a fraction in (0, 1]. Results are kilocalories of estimated excess burn after the bout.
What is EPOC or afterburn?
EPOC means excess post-exercise oxygen consumption: the elevated oxygen and energy cost after exercise while the body recovers. Afterburn is the common name for the same idea expressed as extra calories beyond the workout itself.
What happens if intensity, duration, or weight is missing or non-numeric?
Missing fields, empty strings, non-finite numbers, non-positive duration or weight, and intensity outside the allowed percent or fraction ranges are rejected and not billed.
What units should I use?
Intensity as percent of max effort or a 0–1 fraction, duration in minutes, and weight in kilograms.
What does the EPOC afterburn calculator cost?
The browser tool is free and runs locally.
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/epoc-estimate \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"intensity":80,"duration":45,"weight":70}'const res = await fetch("https://api.kit.forhosting.com/health/epoc-estimate", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"intensity": 80,
"duration": 45,
"weight": 70
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/health/epoc-estimate",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"intensity": 80,
"duration": 45,
"weight": 70
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/health/epoc-estimate", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"intensity":80,"duration":45,"weight":70}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"intensity":80,"duration":45,"weight":70}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/health/epoc-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
{
"intensity": 80,
"duration": 45,
"weight": 70
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "health.epoc_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
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
Missing fields and non-numeric values fail with invalid_input so bad form data never masquerades as recovery science.
How the linear EPOC afterburn model works
Algebraically that is epoc_kcal equals two point five times intensity_fraction times duration_minutes over sixty times weight_kg. The hourly rate at the stated intensity is two point five times intensity_fraction times weight, here one hundred forty kilocalories per hour of excess cost, and three quarters of an hour is three quarters of that rate. The response echoes cleaned inputs, intensity as both percent and fraction, duration in minutes and hours, the coefficient K, epoc in kilocalories and kilojoules, and a formula string so every factor is auditable. Zero or negative duration or weight, missing intensity, and intensity above one hundred percent fail early with invalid_input rather than inventing absolute values or silent zeros. This is an educational energy-balance planning estimate, not a chamber calorimetry measurement and not a guarantee of fat loss, which also depends on diet, recovery, total daily expenditure, and individual physiology.
What you send and what you get back
Send three fields. All three fields are required. Classic checks include eighty percent intensity at seventy kilograms for forty-five minutes yielding one hundred five kcal, and full intensity at sixty kilograms for sixty minutes yielding one hundred fifty kcal. If you need calories burned during the bout itself rather than post-exercise excess, use a MET calories burned calculator; if you need resting metabolic rate, use a dedicated BMR tool. Those are separate search intents and landings. The field intensity is relative effort as a finite number: either a percent greater than zero and at most one hundred, or a fraction in the interval greater than zero and at most one; aliases include intensity_percent, effort, relative_intensity, pct, and intensity_pct. The field duration is bout length in minutes, finite and strictly greater than zero, with aliases duration_min, duration_minutes, minutes, time, and mins. The field weight is body mass in kilograms, finite and strictly greater than zero, with aliases weight_kg, kg, mass, and body_weight. Missing fields, empty strings, non-numeric values, booleans, NaN, Infinity, non-positive duration or weight, and intensity outside the allowed percent or fraction ranges fail with invalid_input and are not charged. On success the response includes epoc_kcal as the cleaned excess calorie estimate, epoc_kj using the thermochemical factor four point one eight four kilojoules per kilocalorie, unit set to kcal, intensity_percent and intensity_fraction, duration_minutes and duration_hours, weight_kg, kcal_per_hour_at_intensity as the excess rate for the stated effort, coefficient_k equal to two point five, plus formula and method strings documenting the linear intensity-duration-weight path. Pricing for successful API calls is the published base of $0.002 per item; validation failures do not consume prepaid balance.
Where EPOC afterburn calculators show up in real work
Curriculum authors building interactive lessons need the same JSON shape offline and online so worksheets and auto-graders stay aligned. Because this capability is a pure parse engine, API pricing is the published base of $0.002 per successful item and failed validation does not consume balance.
Integration use cases
App and API session afterburn
Bulk-estimate post-workout excess calories for uploaded activity rows with the same linear formula as the free browser tool; reject missing or non-numeric inputs with invalid_input.