What Is a BMR Calculator?
A BMR (Basal Metabolic Rate) calculator estimates how many calories your body burns just to keep you alive at complete rest — breathing, circulating blood, and running basic cellular processes, with no activity or digestion included.
How to Use the BMR Calculator
- Select your sex.
- Choose US or metric units.
- Enter your age, weight, and height.
- Your BMR and estimated daily calorie needs at various activity levels appear instantly.
BMR Formula (Mifflin-St Jeor Equation)
This calculator uses the Mifflin-St Jeor equation, widely considered one of the most accurate BMR formulas for the general population, replacing the older Harris-Benedict equation in most clinical guidelines.
Worked Example
Weight: 160 lb ≈ 72.6 kg
Height: 5'8" = 68 in ≈ 172.7 cm
BMR = 10 × 72.6 + 6.25 × 172.7 − 5 × 30 + 5 ≈ 1,653 calories/day
Understanding Your Results
Your BMR alone isn't your total calorie need — it's just the baseline for staying alive at rest. The table above multiplies your BMR by standard activity factors to estimate your Total Daily Energy Expenditure (TDEE), the number of calories you actually burn including movement, exercise, and daily activity.
Tips for Using Your BMR
- Use your TDEE (activity-adjusted number), not raw BMR, when planning your daily calorie intake.
- To lose weight, most guidelines suggest a moderate deficit (~500 calories/day) below TDEE for roughly 1 lb/week of loss.
- Don't eat below your BMR long-term — it can slow metabolism and isn't a sustainable approach.
Common Mistakes to Avoid
- Confusing BMR (calories at rest) with TDEE (total calories burned including activity).
- Assuming BMR formulas are perfectly precise — they're population averages and can vary ±10% for individuals.
- Ignoring changes in BMR that come with muscle gain, aging, or significant weight change over time.
Frequently Asked Questions
Basal Metabolic Rate is the number of calories your body needs at complete rest just to maintain vital functions like breathing and circulation.
BMR is calories burned at rest. TDEE (Total Daily Energy Expenditure) adds in calories burned through daily activity and exercise, giving a more complete picture of your actual calorie needs.
The Mifflin-St Jeor equation, used in this calculator, is generally considered more accurate for most people than the older Harris-Benedict formula.
Yes — muscle tissue burns more calories at rest than fat tissue, so people with more lean muscle mass generally have a higher BMR.
No — eating at or below your BMR long-term isn't recommended, since it doesn't account for the energy you need for daily activity. Use your activity-adjusted TDEE instead as a baseline for calorie planning.
Yes, BMR typically declines gradually with age, partly due to natural loss of muscle mass, which is one reason calorie needs often decrease later in life.