Calories Burned Calculator
Calories burned in a workout from the activity's MET value, your body weight and the duration (2011 Compendium of Physical Activities).
Result
MET × body weight (kg) × hours, the 2011 Compendium convention. Gross calories: the net figure removes the 1 MET you would burn at rest anyway.
The same 45 minutes, other activities
At 78 kg, gross calories.
How far off can this be?
The calculator uses the standard convention that 1 MET is 1 kcal per kg per hour. In 769 healthy adults, measured resting energy expenditure averaged 0.84 kcal per kg per hour (give or take 0.16), so the convention overestimated it by 20% on average. The authors recommend correcting MET estimates with a person's measured or predicted resting rate.
For the example (78 kg, 45 minutes at 7.5 METs), the calculator gives 439 kcal. Corrected to that sample's average resting rate, the same session is 369 kcal.
The study tested the correction on walking at 5.6 km/h, not on harder exercise. Body composition explained most of the difference in resting rate (62% of the variance), so the correction for one person can be smaller or larger than the average; a measured resting rate removes the guess.
Source: Byrne, Hills, Hunter, Weinsier & Schutz 2005, J Appl Physiol, “Metabolic equivalent: one size does not fit all” .
How to use it
- Pick an activity to fill in its 2024 Adult Compendium MET value, or type a MET yourself, then enter body weight and duration. Burn scales with body weight: a 200 lb person burns about a third more than a 150 lb person in the same workout.
- Read the gross calories, the hourly rate, and the net figure: the calories above the roughly 1 MET you would have burned at rest anyway.
- Treat the result as an estimate: Compendium METs are adult averages, and fitness, technique, terrain and how steady the effort was move a real session up or down.
- Do not eat the number back one for one. Your TDEE activity level already counts your usual training, and the net figure is the fairer one to set against food.
- Cardio burns less than most people expect: 40 minutes of running at 5 mph (8.5 MET) at 160 lb is about 410 calories. For walking at a set speed and incline, the Walking Calorie Calculator uses the ACSM walking equation.
Questions people usually ask
Why is calorie burn only an estimate?
Because calorie burn depends on body size, efficiency, effort, terrain, and movement style. Any calculator is giving you a useful range, not a lab reading.
Why do wearables and calculators disagree?
They use different models and different signals. The useful move is to look for a consistent range instead of chasing a single exact number.
Should I eat back every calorie this shows?
Usually not. Most people do better treating exercise calories cautiously, then adjusting from bodyweight and recovery data over time.
What makes the estimate more useful?
Using realistic duration and effort, then comparing multiple sessions so you understand relative output instead of obsessing over one workout.
Is this tool free and private to use?
Yes. AI Fit Hub tools are free, no-signup browser tools. Inputs stay in your browser unless you choose to share a URL.
Do these tools replace medical guidance?
No. These outputs are general fitness estimates — not medical advice.
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By goal
Use it from an agent or code
Any agent can run this calculator by URL: put the inputs in the query string and get JSON back, with the inputs that used defaults and a line to cite (add format=md for markdown). MCP clients reach it through https://aifithub.io/mcp.
In code, import the same module; it runs where you import it, with no request or key.
import { compute } from "https://aifithub.io/engines/calories-burned-calculator.js";Input and output contract, TypeScript types and the guide for agents.