BMR Calculator
Calculate your Basal Metabolic Rate — the calories you burn at rest — using the Mifflin–St Jeor equation, plus your total daily needs.
BMR is the calories your body burns at complete rest. Multiply by an activity factor for total daily needs (TDEE). Estimates only, not medical advice.
How to use this calculator
Enter your biological sex, age, height (in feet and inches), and weight (in pounds). The calculator immediately returns your BMR — the calories you burn lying still in a fasted state. If you also select an activity level, it shows your TDEE, the total daily burn that accounts for movement and exercise.
How your body burns calories at rest
Even when you are completely still, your body is far from idle. Every heartbeat, breath, and cell division consumes energy. Your organs — particularly the liver, brain, heart, and kidneys — account for the largest share of this resting burn. Skeletal muscle also contributes meaningfully: the more lean mass you carry, the higher your BMR tends to be.
BMR is influenced by several factors you can measure (size, age, sex) and some you cannot easily measure (thyroid hormone levels, body composition, genetics). The Mifflin–St Jeor equation captures the measurable factors and has been validated as one of the most accurate predictive equations for most healthy adults.
From BMR to TDEE — adding activity
BMR is only the resting component. Nearly everyone burns more than that through daily life. The activity multipliers used to convert BMR to TDEE are:
- Sedentary (×1.2) — desk job, little to no formal exercise
- Lightly active (×1.375) — light exercise or walking 1–3 days per week
- Moderately active (×1.55) — moderate exercise 3–5 days per week
- Very active (×1.725) — hard training 6–7 days per week
- Extra active (×1.9) — very hard training or a physically demanding job
Most people slightly overestimate how active they are. When in doubt, choose one level lower than feels right and adjust after a few weeks of tracking.
Worked example — step by step
Consider a 35-year-old woman, 5 feet 6 inches (167.6 cm) and 145 lb (65.8 kg).
- 10 × 65.8 = 658
- 6.25 × 167.6 = 1,047.5
- 5 × 35 = 175
- BMR = 658 + 1,047.5 − 175 − 161 = ≈ 1,370 calories
With moderate activity (×1.55), her TDEE is roughly 1,370 × 1.55 = ≈ 2,120 calories per day. To lose about 1 lb per week she would target approximately 1,620 calories (a 500-calorie deficit).
How to interpret your result
Your BMR is the floor — the minimum calories needed to keep your body running. Never eat below your BMR for extended periods without medical supervision, as severe restriction impairs organ function and can trigger adaptive metabolic slowdown. Your TDEE is a more practical target: eat at TDEE to maintain, modestly below it to lose, and modestly above it to gain.
Common mistakes to avoid
- Eating at BMR instead of TDEE. BMR does not account for any activity. Using it as your daily calorie target is too aggressive a deficit for most people.
- Overestimating activity level. Choosing "very active" when your lifestyle is moderately active inflates your calorie target and can stall fat loss.
- Assuming BMR is fixed. BMR shifts with changes in body weight and composition. Recalculate every 10–15 lb of weight change or every few months to keep targets accurate.
- Ignoring lean mass. BMR formulas use total body weight, not lean mass. If you lose significant muscle alongside fat, your actual resting burn will drop more than the formula predicts.
The formula
Men: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5
Women: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161
TDEE = BMR × activity factor
Results are estimates for general informational purposes, not medical advice. Consult a registered dietitian or physician for individualized nutrition guidance.
How we calculate this
BMR is estimated with the Mifflin–St Jeor equation: 10×kg + 6.25×cm − 5×age + 5 for men, and the same minus 161 for women. Estimates only; not medical advice.
Sources
Frequently asked questions
What is BMR?
Basal Metabolic Rate is the number of calories your body burns at complete rest to sustain essential functions — breathing, circulation, temperature regulation, and cell repair. It typically accounts for 60–70% of your total daily calorie expenditure.
How is BMR calculated?
This calculator uses the Mifflin–St Jeor equation, which research has found to be among the most accurate for most adults. For men: 10×kg + 6.25×cm − 5×age + 5. For women: the same formula minus 161. The result is your resting calorie burn in calories per day.
What is the difference between BMR and TDEE?
BMR is the calories your body needs at complete rest. TDEE (Total Daily Energy Expenditure) is your BMR multiplied by an activity factor that accounts for daily movement and exercise. TDEE is always higher than BMR and represents your actual daily calorie burn.
How do I use my BMR to set a calorie goal?
BMR alone is rarely the right target — almost everyone burns more than BMR through daily life. Use your TDEE (BMR × activity factor) as your maintenance level, then eat below it to lose weight or above it to gain. Our calorie and TDEE calculators make this step easy.
Does BMR change over time?
Yes. BMR decreases with age and with loss of muscle mass, because muscle tissue burns more calories at rest than fat tissue does. Regular resistance training helps preserve lean mass and keep BMR from declining as quickly as it otherwise would.
Is the Mifflin–St Jeor equation accurate for everyone?
It is accurate within roughly 10% for most healthy adults, but it can be less precise for very lean, very muscular, or very obese individuals. People with thyroid disorders or other metabolic conditions may also see bigger deviations. Treat the result as a reliable estimate, not a precise measurement.
What is the Harris–Benedict equation and how does it compare?
Harris–Benedict (1919, revised 1984) is an older BMR formula that tends to overestimate calorie needs by about 5% compared to Mifflin–St Jeor. Most nutrition professionals and dietitians now prefer Mifflin–St Jeor because a 2005 comparison found it to be more accurate for a broader population.