Four formulas, one screen
See Mifflin-St Jeor, Harris-Benedict, Katch-McArdle and Cunningham together. When they agree, you can be confident. When they differ, you learn why.
Free health tool · 4 scientific formulas
BMR Calculator
Use this free BMR calculator to find your basal metabolic rate: the calories your body burns at complete rest just to keep you alive. Compare four proven formulas side by side, then turn your result into a daily calorie target you can actually use.
- 4 formulas compared
- Metric & imperial
- Body-fat precision
- Calorie goals
- Private, nothing stored
Calculate your basal metabolic rate
Your basal metabolic rate
kcal/day
Using Mifflin-St Jeor: calories burned at complete rest.
- Kilojoules
- 7,108 kJ/day
- Per hour
- 71 kcal/hour
- TDEE
- 2,336 kcal/day
Formula comparison
Daily calories for your goal
- Maintain weightKeep your current weight2,336 kcal
- Mild weight lossAbout 0.25 kg per week2,086 kcal
- Weight lossAbout 0.5 kg per week1,836 kcal
- Mild weight gainAbout 0.25 kg per week2,586 kcal
- Weight gainAbout 0.5 kg per week2,836 kcal
Calories by activity level
Features
Why this BMR calculator gives you a better answer
Most BMR calculators run one formula and stop at a single number. This one shows the full picture, so you can trust the result and act on it straight away.
Body-fat precision
Add your body fat percentage and the tool unlocks lean-mass formulas. They are often more accurate for athletes and very muscular people.
Goal-ready calories
Your BMR becomes real targets for maintenance, fat loss and lean gain. The tool also warns you if a target drops below your BMR.
Metric or imperial
Enter cm and kg, or feet, inches and pounds. Your values convert instantly when you switch, so you never have to retype anything.
Instant and private
Everything runs in your browser. Nothing is uploaded or saved, and every result updates the moment you change a value.
Copy and share
Copy a clean summary for your notes, or share a link that reopens the calculator with your exact inputs for a coach or friend.
How it works
How to use the BMR calculator
It takes less than a minute. Follow these five steps and the BMR calculator shows your resting burn, a formula comparison and calorie targets.
Choose units and sex
Pick metric or imperial, then select the sex the formulas should use.
Enter your body stats
Add your age, height and weight. Weigh yourself in the morning for the most consistent number.
Add body fat if known
A DEXA scan, smart scale or tape method works. It unlocks the lean-mass formulas.
Pick a formula
Mifflin-St Jeor suits most adults. Choose Katch-McArdle if you are lean and muscular.
Set your activity
Select how active you are to turn your BMR into daily calorie targets for your goal.
The science
BMR formulas explained
Each equation predicts resting energy from body size. However, researchers built them on different groups of people, so each one suits a slightly different user.
Mifflin-St Jeor
1990 · RecommendedMen10W + 6.25H − 5A + 5
Women10W + 6.25H − 5A − 161W is weight in kg, H is height in cm and A is age in years. A 2005 systematic review found it the most reliable equation for healthy adults, so it is our default.
Harris-Benedict (revised)
1984Men88.362 + 13.397W + 4.799H − 5.677A
Women447.593 + 9.247W + 3.098H − 4.330AThis is the classic 1919 equation, updated by Roza and Shizgal. It often reads a little higher than Mifflin-St Jeor, so it works well as a second opinion.
Katch-McArdle
Lean massBMR370 + 21.6 × LBMLBM is lean body mass in kg, which equals weight × (1 − body fat %). Because it skips age and sex, it works best when you know your body fat.
Cunningham
AthletesBMR500 + 22 × LBMIt also uses lean mass but predicts a higher number. For that reason, coaches often use it for athletes with a lot of muscle and heavy training.
Know the terms
BMR vs RMR vs TDEE: what is the difference?
These three terms sound alike, but they answer different questions. Here is how they compare.
| Term | What it measures | Typical size |
|---|---|---|
| BMR | Energy for vital functions at complete rest, after an overnight fast and sleep | The lowest of the three |
| RMR | Resting energy under looser test conditions | Slightly above BMR |
| TDEE | BMR plus daily movement, exercise and digesting food | BMR × 1.2 to 1.9 |
In practice, BMR and RMR are close enough to use interchangeably. TDEE is the number to eat around, and our TDEE calculator breaks it down further.
Key factors
What affects your basal metabolic rate?
Your BMR is not fixed. Several factors push it up or down, and some of them are within your control.
- Lean muscle mass. Muscle burns more energy at rest than fat, so more muscle means a higher BMR.
- Body size. Taller and heavier people have more tissue to maintain, so they burn more.
- Age. BMR usually falls with age, largely because muscle declines. Mifflin-St Jeor removes 5 kcal for each year.
- Sex. Men usually have a higher BMR at the same size because they carry more lean mass on average.
- Hormones and health. Thyroid hormones, illness and some medicines can raise or lower your metabolism.
- Dieting history. Long, aggressive calorie cuts can lower energy use, a process called adaptive thermogenesis.
Example BMR by age
| Age | Men | Women |
|---|---|---|
| 20 | 1,699 kcal | 1,352 kcal |
| 30 | 1,649 kcal | 1,302 kcal |
| 40 | 1,599 kcal | 1,252 kcal |
| 50 | 1,549 kcal | 1,202 kcal |
| 60 | 1,499 kcal | 1,152 kcal |
| 70 | 1,449 kcal | 1,102 kcal |
Benefits
Benefits of knowing your BMR
Your BMR is the foundation of every smart nutrition plan. Here is what it helps you do.
Set a realistic target
Your BMR is the floor under your daily calories. Knowing it stops you from picking a diet too harsh to sustain.
Lose fat, keep muscle
A moderate deficit from your TDEE, not your BMR, helps protect lean mass and your energy levels.
Plan muscle gain
A small surplus above maintenance supports strength training without piling on unnecessary fat.
Track progress
Recalculate as your weight or body fat changes, so your calorie targets stay accurate over time.
FAQ
BMR calculator FAQs
Quick answers to the questions people ask most about basal metabolic rate.
What is a normal BMR?
There is no single normal value, because BMR depends on your size, age and sex. Many adult women land roughly between 1,200 and 1,500 kcal a day, while many adult men land between 1,500 and 1,900 kcal. So compare your result with the example table above rather than with other people.
How do you calculate BMR?
Most calculators use the Mifflin-St Jeor equation: 10 × weight (kg) + 6.25 × height (cm) − 5 × age, then add 5 for men or subtract 161 for women. For example, a 30-year-old man who is 175 cm tall and weighs 75 kg has a BMR of about 1,699 kcal per day.
Which BMR formula is the most accurate?
For most healthy adults, Mifflin-St Jeor gives the most reliable estimate. However, if you know your body fat and you are lean or muscular, Katch-McArdle is often closer. Only a lab test called indirect calorimetry measures your metabolic rate directly.
Should I eat less than my BMR to lose weight?
Usually not. It is safer to eat below your TDEE but at or above your BMR. Very low intakes can cost you muscle, energy and nutrients, so talk to a doctor or dietitian before you go lower.
How many calories do I burn a day?
Multiply your BMR by an activity factor from 1.2 for sedentary people up to 1.9 for extra active people. The result is your TDEE, and the calculator shows it for every activity level.
Does BMR decrease with age?
Yes. BMR tends to fall slowly as you get older, mainly because people lose muscle. Regular strength training and enough protein help slow that decline.
How can I increase my BMR?
Build muscle with resistance training, eat enough protein, sleep well and avoid long crash diets. Together, these habits support a higher resting metabolism over time.
How accurate is this BMR calculator?
Formula estimates usually land within about 10 percent of measured values for most people. Your true BMR can differ because of genetics, muscle mass and health conditions. Therefore, treat the result as a starting point and adjust it based on your real progress.
Start with your BMR, then build your plan
Your basal metabolic rate is the base of every calorie plan. Use the BMR calculator above to find it, compare the formulas and set a daily target that fits your goal. Then fine-tune your plan with the tools below.
Calculate my BMRThis BMR calculator gives estimates for healthy adults and is not medical advice. If you are pregnant, under 18 or managing a health condition, ask a qualified professional before you change your diet.