This BMR calculator estimates your basal metabolic rate, the number of calories your body burns in 24 hours if you did nothing but rest. Enter age, sex, height (cm) and weight (kg); the tool shows the result from three formulas so you can see how much they agree.
BMR is the floor of your energy needs, not your eating target. To find what to eat, the BMR is multiplied by an activity factor, which the TDEE calculator does for you.
Quick numbers
Main formula
Mifflin St JeorWoman, 30, 60 kg, 160 cm
1,289 kcal a dayMan, 30, 70 kg, 175 cm
1,649 kcal a dayChange per year of age
about 5 kcal lessShare of daily energy
about 60 to 70 percent
What BMR means in plain words
Even lying still, your body is busy. The heart beats about 100,000 times a day, the brain uses close to a fifth of resting energy, and the liver and kidneys clean the blood nonstop. BMR measures the fuel all that work needs.
It is measured in a lab after an overnight fast, lying down in a warm, quiet room. Calculators estimate it from body size, age and sex, because these explain most of the difference between people.
BMR calculator formula: Mifflin St Jeor
Men: BMR = 10 × kg + 6.25 × cm − 5 × age + 5
Women: BMR = 10 × kg + 6.25 × cm − 5 × age − 161
A man of 30 who is 175 cm and 70 kg: 700 + 1,093.75 − 150 + 5 = 1,649 kcal a day.
This equation was published by researchers who compared older formulas with measured energy use, and it came out the most accurate for healthy adults of normal weight and with obesity. It is the default in the calculator above.
Harris Benedict and Katch McArdle
The revised Harris Benedict formula is older and tends to give a slightly higher result. For the woman in our example it gives about 1,368 kcal compared with 1,289 from Mifflin St Jeor.
Katch McArdle uses lean body mass instead of total weight: BMR = 370 + 21.6 × lean mass in kg. It suits people who know their body fat percentage. A 70 kg man with 18 percent body fat has about 57.4 kg of lean mass and a BMR near 1,610 kcal. Get a body fat estimate from the body fat calculator.
BMR for men and women by age
| Age | Woman, 160 cm, 60 kg | Man, 175 cm, 70 kg |
|---|---|---|
| 20 | 1,339 | 1,699 |
| 30 | 1,289 | 1,649 |
| 40 | 1,239 | 1,599 |
| 50 | 1,189 | 1,549 |
| 60 | 1,139 | 1,499 |
BMR falls by about 5 kcal a day for every year of age in the formula. In real life the drop comes mostly from losing muscle, which strength training two or three times a week can slow.
Using your BMR to lose or gain weight
Do not eat at your BMR to lose weight. Eating only your resting needs leaves nothing for movement, and you will feel tired and hungry. Instead, find your maintenance from the calorie calculator, then take off 300 to 500 kcal.
To gain, add 250 to 500 kcal to maintenance, as the page on gaining weight explains. People searching for a BMR calculator to gain weight should follow the same path: BMR first, then activity, then the surplus. In both cases, keep protein up so the change comes from fat, not muscle.
What raises or lowers your BMR
- Muscle mass: each kilogram of muscle uses more energy at rest than a kilogram of fat.
- Body size: taller and heavier people have higher BMR.
- Age: BMR drops slowly from the twenties onward.
- Thyroid hormones: an underactive thyroid can lower BMR; an overactive one raises it.
- Fever and illness: a fever raises energy use by roughly a tenth or more for each degree Celsius.
- Very low calorie diets: the body adapts and spends a bit less.
If you feel cold, tired and keep gaining weight while eating little, ask a doctor to check your thyroid rather than cutting more food.
BMR vs TDEE vs RMR
| Term | What it counts | Typical size |
|---|---|---|
| BMR | Energy at complete rest after a fast | Base |
| RMR | Resting energy, measured less strictly | Up to 10 percent above BMR |
| TDEE | BMR plus food digestion and all movement | 1.2 to 1.9 times BMR |
The BMR TDEE calculator formula is simply the two steps joined: Mifflin St Jeor for BMR, then the activity factor. People often use BMR and RMR as if they were the same. For everyday planning the difference does not matter. TDEE is the number you eat to; see the TDEE calculator.
Frequently asked questions
What is a good BMR for a woman?
There is no good or bad BMR; it reflects body size. A 30 year old woman of 160 cm and 60 kg has a BMR of about 1,290 kcal by the Mifflin St Jeor formula.
How do I use a BMR calculator to lose weight?
Find your BMR, multiply it by your activity factor to get maintenance, then eat 300 to 500 kcal less. Do not eat below your BMR for long without a doctor or dietitian.
Is BMR higher in men?
Yes, at the same height, weight and age, because men usually carry more muscle. The formula adds 5 for men and subtracts 161 for women.
Is a BMR calculator for a female different?
Only by the constant. The female version of Mifflin St Jeor subtracts 161 where the male one adds 5, so a woman's BMR comes out 166 kcal lower at the same height, weight and age.
Which BMR formula is most accurate?
For most healthy adults, Mifflin St Jeor. If you know your body fat percentage well, Katch McArdle can be closer, especially for lean, muscular people.
Can I increase my BMR?
A little. Building muscle with strength training raises it, and so does being more active through the day. Supplements that claim to boost metabolism make little real difference.
Does BMR include exercise?
No. BMR is resting energy only. Exercise and daily movement are added on top to give TDEE.
Sources
- Mifflin St Jeor equation
- Harris Benedict equation, revised
- Katch McArdle equation