---
title: "Calorie and BMR calculator — free, runs in your browser"
description: "Resting metabolic rate and daily calorie needs by activity level. Free, no sign-up, and nothing you enter leaves your browser."
url: https://atoneplace.net/tools/calorie-calculator/
site: "At One Place"
---

# Calorie and BMR calculator

Resting metabolic rate and daily calorie needs by activity level.

## How it works

Estimates resting metabolic rate using the Mifflin–St Jeor equation, then scales it by an activity factor to give daily maintenance calories.

Mifflin–St Jeor is used here because it has held up better than the older Harris–Benedict equation in validation studies, typically landing within about 10% of measured resting expenditure for most adults. That 10% is the point worth taking seriously: an estimate this far out is a starting figure to adjust from, not a target to hit.

The activity multipliers are the weakest part of any such calculator. Self-reported activity is unreliable in a consistent direction — people overestimate it — and the gap between the sedentary and moderately-active multipliers is several hundred calories a day. If the numbers here do not match what you observe over a few weeks, trust the observation.

This is arithmetic on a published equation, not dietary advice. Individual metabolic rates vary for reasons no equation captures, and anyone managing a medical condition should be working from clinical guidance rather than a web page.

> This tool runs entirely in your browser. Nothing you enter is sent to a server, logged or stored, and the page keeps working with the network disconnected.

## Common questions

### What is BMR?

Basal metabolic rate: the energy your body uses at complete rest, which for most people is 60–70% of total daily expenditure.

### How accurate is the Mifflin–St Jeor equation?

It typically lands within about 10% of measured resting expenditure for most adults, which makes it a starting estimate rather than a precise figure.

### Which activity level should I choose?

Probably one lower than you think. Self-reported activity is consistently overestimated, and the gap between adjacent multipliers is several hundred calories a day.

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## Sources

- A new predictive equation for resting energy expenditure in healthy individuals — Mifflin et al., American Journal of Clinical Nutrition 51(2), 1990 (https://pubmed.ncbi.nlm.nih.gov/2305711/)