BMR & TDEE Calculator

How to use the bmr & tdee calculator

1. Fill in the fields — they start with a worked example.
2. Read the answer, and the arithmetic shown beneath it.
3. Copy the results, or adjust the inputs to compare scenarios.

About this tool

Basal metabolic rate is roughly what your body uses at complete rest — breathing, circulation, keeping warm. Total daily energy expenditure multiplies that by an activity factor to estimate what you actually burn in a day.

The Mifflin-St Jeor equation is used here because it predicts measured rates more accurately than the older Harris-Benedict formula for most people. Even so, it is a population estimate: individual metabolic rates vary by roughly ±10% around the prediction, and body composition shifts it further, since muscle burns more at rest than fat does.

Treat the result as a starting point to adjust from, not a target to obey.

Common uses

• Getting a starting calorie figure before adjusting by results.
• Understanding how activity level changes daily needs.
• Converting calorie needs into kilojoules for a European label.

Frequently asked questions

How accurate is this?

It predicts measured resting rates within about 10% for most people, and less well at the extremes of body composition. Use it as a baseline and adjust from what actually happens.

Which activity level should I choose?

Most people overestimate. Unless you train hard most days, 'lightly active' is usually closer than 'very active'.