BMR (Basal Metabolic Rate) Calculator
Professional BMR calculator to estimate your Basal Metabolic Rate and daily calorie needs (TDEE) using Mifflin–St Jeor, Harris–Benedict, or Katch–McArdle formulas. Accurate, accessible, and mobile-first.
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Educational purposes only. Not medical advice.
Estimates are rounded. Individual needs vary by genetics, hormones, and body composition.
How to Use This Calculator
Select the measurement system first, then choose your sex, age, height, and weight. Pick the formula that matches the information you have, enter body fat % when using Katch–McArdle, and choose the activity level that best reflects your weekly habits. Click Calculate to refresh BMR and TDEE instantly.
Methodology
The calculator converts every input to kilograms and centimeters, then applies the selected fixed-rate formula to estimate the resting energy need. Activity multipliers and optional body-fat adjustments are applied after the base BMR is computed.
Data Source and Methodology
This calculator implements three peer-reviewed, widely cited equations:
- Mifflin MD, St Jeor ST, et al. A new predictive equation for resting energy expenditure in healthy individuals. American Journal of Clinical Nutrition. 1990;51(2):241–247.
- Harris JA, Benedict FG. A Biometric Study of Basal Metabolism in Man. 1919; revised (Roza & Shizgal, 1984) coefficients clarify the constants used here.
- Katch VL, McArdle WD. Nutrition, Weight Control, and Exercise. Houghton Mifflin; 1977. Fat-free mass based REE estimation.
Refer to the Citations section below for the original sources.
Tutti i calcoli si basano rigorosamente sulle formule e sui dati forniti da questa fonte.
Glossary of Variables
- Age (years)
- Age in whole years.
- Height (cm or ft/in)
- Body height. Converted to centimeters for computation.
- Weight (kg or lb)
- Body mass. Converted to kilograms for computation.
- Body fat %
- Percentage of body weight from fat. Used for Katch–McArdle only.
- BMR (kcal/day)
- Basal Metabolic Rate: calories needed at complete rest.
- TDEE (kcal/day)
- Total Daily Energy Expenditure: BMR multiplied by an activity factor.
How It Works: A Step-by-Step Example
Scenario: Male, 30 years, 180 cm, 75 kg, Moderately active (AF=1.55), formula: Mifflin–St Jeor.
- Compute BMR: \( 10 \times 75 + 6.25 \times 180 - 5 \times 30 + 5 = 750 + 1125 - 150 + 5 = 1730\ \mathrm{kcal/day} \).
- Estimate TDEE: \( 1730 \times 1.55 \approx 2682\ \mathrm{kcal/day} \).
- Mild weight loss target (−15%): \( 2682 \times 0.85 \approx 2280\ \mathrm{kcal/day} \).
- Mild weight gain target (+10%): \( 2682 \times 1.10 \approx 2950\ \mathrm{kcal/day} \).
Frequently Asked Questions (FAQ)
Is BMR the same as RMR?
No. BMR is measured under stricter lab conditions than Resting Metabolic Rate (RMR). Many tools use the terms interchangeably, but BMR estimates are generally slightly lower than RMR.
Which formula should I choose?
Mifflin–St Jeor is a strong default for most adults. If you reliably know your body fat percentage, Katch–McArdle can be very precise. Harris–Benedict is a classic alternative.
How accurate are these estimates?
They’re population-based models. Individual metabolism can deviate due to genetics, hormonal status, medications, and lean mass. Treat results as starting points.
What activity factor should I use?
Pick the one that best reflects your weekly training and occupation. If unsure, start lower and adjust based on weight trends.
Do I need to change calories every day?
Short-term fluctuations are normal. Reassess every 2–4 weeks and adjust calories if average weight changes differ from your target trend.
Can this calculator help with macros?
It focuses on energy needs. For macronutrient planning, use a dedicated macro calculator after establishing TDEE.
Is there a medical restriction?
If you have medical conditions, are pregnant, or under 18, consult a qualified professional. This tool is not medical advice.