About this BMR Calculator
Before calculating how many calories you need to eat to lose weight, you must know your baseline. BMR represents the energy required for basic life functions like breathing, circulation, and cell production. It accounts for about 60-75% of your daily calorie burn.
Who this calculator is for
- Adults estimating how many calories their body uses at complete rest.
- People building calorie targets for fat loss, maintenance, or muscle gain.
- Anyone who wants a baseline before calculating TDEE or macros.
When to use it
- Use this calculator to estimate resting calorie needs before setting a diet target.
- Use it when comparing how age, body size, or sex changes baseline metabolism.
- Use it as the starting point for TDEE, macro, and protein planning.
How to use this calculator
- Select your Gender (physiology affects metabolism).
- Enter your Age, Height, and Weight.
- The calculator applies the Mifflin-St Jeor formula.
- The result is your daily calorie burn if you did absolutely nothing (comatose state).
Key assumptions
- The estimate uses the Mifflin-St Jeor equation, which is intended for the general adult population.
- BMR reflects calories burned at rest, not a full day of normal movement or exercise.
- Body composition, illness, and hormonal factors can shift real metabolic needs above or below the estimate.
Accuracy and testing
Review formula sources, default test cases, assumptions, unit handling, rounding rules, and changelog for this calculator.
How this calculator works
Mifflin-St Jeor Equation:
* Men: (10 × weight in kg) + (6.25 × height in cm) - (5 × age in years) + 5
* Women: (10 × weight in kg) + (6.25 × height in cm) - (5 × age in years) - 161
Inputs explained
Age
Metabolism naturally slows down as you age due to hormonal changes and muscle loss.
Gender
Men typically have higher muscle mass and lower body fat than women, resulting in a higher BMR.
Understanding your results
Your BMR is your minimum caloric requirement. To maintain weight, you must eat *more* than this to account for movement (see TDEE). Eating *below* your BMR for extended periods can slow your metabolism.
Example scenarios
Average Male
Age 30, 5'10", 180 lbs. BMR ≈ 1,815 calories/day.
Average Female
Age 30, 5'4", 140 lbs. BMR ≈ 1,385 calories/day.
Key Features
- Mifflin-St Jeor Formula
- Imperial/Metric inputs
- Foundation for TDEE
Tips & Best Practices
- The most effective way to increase your BMR is to build lean muscle mass through resistance training.
- Do not confuse BMR with TDEE. BMR is rest only; TDEE includes activity.
- Certain medical conditions (thyroid issues) can alter your actual BMR significantly from the formula.
Glossary of Terms
- Basal Metabolic Rate
- The number of calories required to keep your body functioning at rest.
- Resting Metabolic Rate (RMR)
- Similar to BMR but measured under less strict conditions. Often used interchangeably.