BMR Calculator - Basal Metabolic Rate & Daily Calorie Burn
Find the calories your body burns at complete rest using Mifflin-St Jeor, Harris-Benedict or Katch-McArdle — then see your total daily burn at every activity level.
BMR equations were derived separately for males and females.
Used to turn BMR into your daily calorie burn (TDEE).
Your calorie burn at every activity level
| Activity level | Multiplier | Calories per day |
|---|---|---|
| Sedentary — desk job, little exercise | ×1.2 | 2,039 |
| Lightly active — exercise 1–3 days a week | ×1.375 | 2,336 |
| Moderately active — exercise 3–5 days a week | ×1.55 | 2,633 |
| Very active — hard exercise 6–7 days a week | ×1.725 | 2,930 |
| Extra active — physical job or twice-daily training | ×1.9 | 3,228 |
BMR equations are population averages — your real metabolism can sit 10% either side of the estimate depending on genetics, muscle mass, hormones and medication. Use the number as a starting point and adjust based on how your weight actually responds.
What is BMR?
Basal metabolic rate is the energy your body uses just to stay alive: breathing, circulating blood, maintaining temperature, repairing cells and running your brain. It is measured at complete rest, in a neutral environment, after fasting — so it excludes every calorie burned by movement, digestion or exercise. For most people BMR is 60–70% of total daily energy expenditure, which makes it the largest single component of what you burn.
BMR vs TDEE
BMR is your floor. TDEE — total daily energy expenditure — is what you actually burn across a real day, obtained by multiplying BMR by an activity factor. TDEE is the number you use for nutrition planning: eat at it to maintain weight, below it to lose, above it to gain.
- Sedentary (×1.2) — desk job, little deliberate exercise
- Lightly active (×1.375) — exercise 1–3 days a week
- Moderately active (×1.55) — exercise 3–5 days a week
- Very active (×1.725) — hard exercise 6–7 days a week
- Extra active (×1.9) — physically demanding job or twice-daily training
The Three Formulas Compared
Mifflin-St Jeor
Published in 1990 and generally the most accurate for the general population. The default here.
Harris-Benedict
The original 1919 equation, revised in 1984. Tends to read slightly higher.
Katch-McArdle
Uses lean body mass instead of total weight — better for lean, muscular people.
Mifflin-St Jeor (men): 10 × kg + 6.25 × cm − 5 × age + 5
Mifflin-St Jeor (women): 10 × kg + 6.25 × cm − 5 × age − 161
Katch-McArdle: 370 + 21.6 × lean body mass in kg
How to Calculate Your BMR
- Choose metric or imperial units.
- Enter your sex, age, height and weight.
- Select a formula — or leave Mifflin-St Jeor selected.
- If using Katch-McArdle, enter your body fat percentage.
- Pick your activity level to get your TDEE.
- Compare all three formulas and every activity level in the tables below.
What Actually Determines Your BMR
- Lean body mass — the dominant factor. Muscle, organs and bone are metabolically active; stored fat is much less so.
- Body size — larger bodies simply require more energy to maintain.
- Age — BMR declines gradually through adulthood, largely because lean mass tends to fall.
- Sex — average differences in body composition, which is why the equations use different constants.
- Genetics, hormones and medication — thyroid function in particular can shift BMR substantially in either direction.
Can You Increase Your Metabolism?
Partly. BMR itself is mostly set by size, composition, age and genetics, so the honest answer is that you cannot change it dramatically. What you can change is total daily burn: adding lean muscle raises the resting figure modestly, and moving more throughout the day raises the activity component substantially. Non-exercise movement — walking, standing, fidgeting — varies by hundreds of calories a day between individuals and is the most underrated lever available.
Note also that BMR falls somewhat during a prolonged calorie deficit, as the body adapts to a smaller size and lower energy availability. That is one reason weight loss slows over time even when intake stays constant.
How Accurate Are These Estimates?
Predictive equations estimate BMR within roughly 10% for most people, but individuals can sit well outside that. The only precise measurement is indirect calorimetry in a clinical setting. The practical approach is to treat the calculated figure as a starting point, hold intake steady for two to three weeks, track weight, and adjust based on what actually happens rather than what the equation predicted.
Who This Calculator Is For
- Anyone planning a calorie target for weight loss or gain
- Gym-goers estimating their daily energy needs
- People tracking macros who need a starting calorie figure
- Coaches and trainers setting client baselines
- Anyone curious how much energy their body uses at rest
❓ Frequently Asked Questions
What is BMR?
Basal metabolic rate is the energy your body uses at complete rest just to stay alive — breathing, circulation, brain function and cell repair. It is typically 60–70% of your total daily calorie burn.
What is the difference between BMR and TDEE?
BMR is your resting burn. TDEE — total daily energy expenditure — is BMR multiplied by an activity factor to include movement, exercise and digestion.
Which BMR formula is most accurate?
Mifflin-St Jeor is generally the most accurate for the general population and is the default here. Katch-McArdle can be better for lean, muscular people because it uses lean body mass instead of total weight.
What is the Mifflin-St Jeor equation?
For men: 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5. For women the final term is −161 instead of +5.
What is the Katch-McArdle formula?
BMR = 370 + 21.6 × lean body mass in kilograms. It requires a body fat percentage, which is why it is only available when you provide one.
Which activity multiplier should I choose?
Sedentary (1.2) for a desk job with little exercise, lightly active (1.375) for 1–3 sessions a week, moderately active (1.55) for 3–5, very active (1.725) for 6–7, and extra active (1.9) for physical work or twice-daily training.
Why do men and women have different BMRs?
Because of average differences in body composition — more lean mass burns more energy at rest. The equations reflect this with different constants.
Does BMR fall with age?
Yes. It typically declines gradually, largely because lean muscle mass tends to decrease. Resistance training helps slow that decline.
Can I speed up my metabolism?
You can raise your total burn by adding muscle, moving more throughout the day and exercising, but BMR itself is largely set by size, body composition, age and genetics.
Is this medical advice?
No. These are population estimates that can be 10% off for any individual. Consult a healthcare professional or dietitian for personalised guidance.