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BMR Calculator

Calculates Basal Metabolic Rate — the calories your body burns at complete rest — using the Mifflin-St Jeor equation.

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In short BMR Calculator is a free online tool on inputtesthub.com that calculates Basal Metabolic Rate — the calories your body burns at complete rest — using the Mifflin-St Jeor equation. It needs no account, no download and no payment, and there is no daily usage limit. Everything is processed inside your own browser, so the data you paste is never uploaded to a server.

How to use the BMR Calculator

  1. Enter your figures in the input fields.
  2. The result updates as you type, together with the full working.
  3. Check the breakdown table to see exactly how the number was reached.

About the BMR Calculator

The BMR Calculator calculates Basal Metabolic Rate — the calories your body burns at complete rest — using the Mifflin-St Jeor equation. It runs as plain JavaScript inside the page, which means there is no upload step, no queue and no size limit imposed by a server — the only limit is your own device.

What people use it for

  • Working out a calorie floor before setting a deficit.
  • Understanding why two people of the same weight need different amounts.
  • Feeding into a TDEE calculation.

The maths behind it

This tool uses the Mifflin-St Jeor equation: 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5 for men, and the same with −161 for women. It replaced Harris-Benedict as the more accurate estimator in modern populations. Every intermediate value is shown on screen, so the result can be checked by hand.

BMR equations estimate an average for your height, weight, age and sex. Individual metabolic rate can vary by 10% or more either way. Use it as a starting point and adjust based on what actually happens to your weight over a few weeks.

Frequently asked questions

Is the BMR Calculator free, or is there a paid tier?
Free, unlimited, and no email address required. You can use it a hundred times a day and nothing changes.
Is my data uploaded anywhere?
No. The BMR Calculator runs entirely in your browser using JavaScript. Nothing is transmitted, logged or stored, which you can verify yourself in the Network tab of your browser's developer tools.
How is the result calculated?
It uses the Mifflin-St Jeor equation: 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5 for men, and the same with −161 for women. It replaced Harris-Benedict as the more accurate estimator in modern populations. The full working is printed under the result, so you can follow every step rather than trusting a black box.
What do people use the BMR Calculator for most?
The jobs it is built for: working out a calorie floor before setting a deficit. Understanding why two people of the same weight need different amounts. Feeding into a TDEE calculation. It is built for exactly those cases rather than being a general-purpose tool with this bolted on.
What do people usually get wrong here?
BMR equations estimate an average for your height, weight, age and sex. Individual metabolic rate can vary by 10% or more either way. Use it as a starting point and adjust based on what actually happens to your weight over a few weeks.
Can I rely on this for exact work?
The calculation runs in double precision and the result is shown to ten significant figures, so converting a value and converting it back returns the original. What is displayed is rounded for readability; what is copied is not.

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