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BMR Calculator — Basal Metabolic Rate (Metric & Imperial)

Calculate your BMR quickly using Mifflin or Katch (with body fat). Get your resting calories to plan weight loss, maintenance, or gain.

  • Compare Mifflin-St Jeor and Katch-McArdle side by side.
  • Use your body-fat percentage to unlock a lean-mass calculation.
  • Get instant calorie targets for maintenance, deficit, or surplus.

Your details

Sex
Units
Body-fat % (optional)

What the BMR calculator tells you

Basal metabolic rate (BMR) is the energy your body spends to keep you alive at complete rest. It covers breathing, circulation, and organ function—not your workouts.

Our calculator uses the Mifflin-St Jeor equation by default. Add your body-fat percentage and we show Katch-McArdle, which adjusts for lean mass and helps athletes plan with more precision.

With this page you can:

BMR abbreviations in plain language

Here’s a quick glossary for the acronyms you’ll see on this page.

BMR
Basal Metabolic Rate—calories burned at complete rest.
RMR
Resting Metabolic Rate—similar to BMR but measured while awake and relaxed.
Lean mass
Your body weight minus fat mass. Katch-McArdle uses this to refine the estimate.

Need a deeper explanation?

Read the BMR guide to understand why the equations differ, how to measure inputs accurately, and when to adjust your calorie targets.

Read the BMR guide

BMR FAQ

Which BMR formula should I use?

Start with Mifflin-St Jeor. If you know your body-fat percentage, compare it with Katch-McArdle to see how lean mass changes the result.

How often should I recalculate my BMR?

Recalculate when your weight changes by roughly 5% or more, or whenever you update your body-fat percentage.

Is BMR enough to plan calories?

BMR is the foundation. Pair it with activity using the TDEE or daily calories calculators to set a deficit or surplus.

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Need help or have a question?

Email our team and we’ll reply as soon as we can.

support@microsaaslabs.com