Free BMR Calculator Online
This free BMR calculator uses the Harris-Benedict formula to estimate how many calories your body burns at complete rest — your Basal Metabolic Rate. Use it online for both metric and imperial units, completely free.
Basal Metabolic Rate
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What Is BMR?
Your Basal Metabolic Rate (BMR) is the number of calories your body burns to keep itself alive while you do absolutely nothing. Breathing, heartbeat, maintaining body temperature, cell repair — all of it costs energy. This free online BMR calculator quantifies that baseline cost instantly.
For most sedentary adults, BMR accounts for 60–75% of total daily calorie expenditure. That means even on a rest day with zero exercise, your body is burning the majority of its daily calories just to exist. Understanding your BMR gives you a realistic floor — a number below which you should almost never eat. Calculate online to see your personal number in seconds.
A 30-year-old male at 175 cm and 75 kg has a BMR of roughly 1,840 calories per day. A woman of the same age and dimensions burns closer to 1,620 calories at rest — a meaningful difference driven by average differences in lean mass. Use this free tool to find your own baseline.
The Harris-Benedict Formula
The revised Harris-Benedict equation (1984) is one of the most widely used BMR formulas:
Men
BMR = 88.362 + (13.397 × kg) + (4.799 × cm) − (5.677 × age)
Women
BMR = 447.593 + (9.247 × kg) + (3.098 × cm) − (4.330 × age)
Weight in kilograms, height in centimeters, age in years.
From BMR to TDEE: Activity Multipliers
Multiply your BMR by the appropriate activity factor to get your Total Daily Energy Expenditure (TDEE) — the actual number of calories you burn each day. Our free online calculator applies this multiplier automatically once you select your activity level.
| Activity Level | Description | Multiplier |
|---|---|---|
| Sedentary | Desk job, little or no exercise | × 1.200 |
| Lightly Active | Light exercise 1–3 days/week | × 1.375 |
| Moderately Active | Moderate exercise 3–5 days/week | × 1.550 |
| Very Active | Hard exercise 6–7 days/week | × 1.725 |
| Extra Active | Physical job + hard training daily | × 1.900 |
Most people overestimate their activity level. When in doubt, choose one level lower than you think — it's more accurate for the majority of desk workers.
How to Use Your BMR Result
Weight Loss
Calculate your TDEE, then subtract 300–500 calories. Never eat below your BMR for sustained periods — it triggers muscle loss and metabolic slowdown.
Maintenance
Match your calorie intake to your TDEE. Your BMR calculator result is the floor; TDEE is your daily target for a stable weight.
Muscle Gain
Add 200–300 calories above TDEE for a lean bulk. Higher surpluses mostly produce fat. Track body composition, not just scale weight.
Factors That Affect Your BMR
The BMR calculator formula uses age, sex, height, and weight — but your actual resting metabolic rate is influenced by several factors the formula can't fully capture.
Lean muscle mass is the biggest variable. Muscle burns about 6 calories per pound per day at rest; fat burns about 2. Two people with the same BMI but different body compositions will have meaningfully different BMRs. This is why formula-based estimates can be off by 10–15% for very muscular or very lean individuals.
Thyroid function directly regulates metabolic rate. Hypothyroidism can lower BMR by 30–40%; hyperthyroidism can raise it significantly. If your weight changes dramatically despite consistent eating, a thyroid panel is worth discussing with your doctor.
Age and hormones play a compounding role. Testosterone and estrogen both support lean muscle retention — as these decline with age, BMR typically follows. Resistance training is the most proven intervention for slowing age-related BMR decline.
Practical Tips for Using Your BMR
Use your BMR as a floor, not a ceiling — never eat below it long-term.
Recalculate your BMR online every 5–10 lbs of weight change for accuracy.
Resistance training is the most effective way to raise your resting BMR.
Consistent sleep (7–9 hours) supports healthy metabolic function.
Frequently Asked Questions
Disclaimer: This free online BMR calculator provides estimates based on the Harris-Benedict formula and is intended for informational purposes only. Individual metabolic rates vary based on factors including body composition, thyroid function, medications, and health conditions. Consult a qualified healthcare provider or registered dietitian before making significant changes to your diet or calorie intake. This free tool does not substitute for professional medical guidance.
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