What basal metabolic rate means
Basal metabolic rate is the energy a body uses at complete rest, in a fasted, thermoneutral state — enough to keep breathing, circulating blood, and running the brain and organs. In everyday talk it is close to resting metabolic rate (RMR). True BMR is measured in clinic with indirect calorimetry. Web calculators estimate it from weight, height, age, and sex.
This page uses Mifflin–St Jeor (1990), the same base equation as the calorie calculator:
Men: 10 × kg + 6.25 × cm − 5 × age + 5
Women: 10 × kg + 6.25 × cm − 5 × age − 161
Worked example
A 50-year-old man, 178 cm, 82 kg:
10×82 + 6.25×178 − 5×50 + 5 = 820 + 1,112.5 − 250 + 5 = 1,688 kcal/day at rest.
That is not a recommended intake. Eating at BMR for weeks is an extreme deficit. To plan a day, open the calorie calculator and apply an activity factor.
What raises or lowers BMR
- More lean mass usually raises it; crash dieting that costs muscle can lower it.
- Age appears in the equation because average resting burn declines across adulthood.
- Fever, pregnancy, and some medicines change energy use in ways a website cannot see.
- Thyroid disease and other endocrine conditions belong with a clinician, not this form.
If you are also looking at weight-for-height, use the BMI calculator and read where BMI falls short. For meals that can sit under a calorie range, see the meal framework.
Frequently asked
Is BMR the same as TDEE?
No. TDEE includes walking, work, and exercise. BMR is the resting floor.
Why is my BMR lower than a friend’s?
Smaller bodies and older ages produce a lower estimate. Muscle mass, which this form cannot measure, also matters.
Should I eat only my BMR to lose fat?
No. That is an extreme cut. Discuss any deficit with a clinician and keep protein and resistance work in the plan.
See also: Wikipedia, “Basal metabolic rate”; Mifflin et al., Am J Clin Nutr 1990.
BMR, RMR, and why the names blur
Laboratories sometimes distinguish basal and resting measurements by how strictly the person fasted and how still they lay. Desk calculators ignore that distinction. Treat this output as an estimate of resting burn, then add movement on the calorie page. Searching “what is BMR” and landing here should still send you onward to TDEE if you want a day of food.
Athletes with large lean mass often measure higher than Mifflin–St Jeor predicts. People who have dieted hard for months often measure lower. The equation cannot see those histories. It sees kg, cm, age, and sex.
A second worked example
A 68-year-old woman, 160 cm, 64 kg: 10×64 + 6.25×160 − 5×68 − 161 = 640 + 1,000 − 340 − 161 = 1,139 kcal at rest. Moderate activity would take that near 1,750. That is still only planning maths. Medicines, illness, and joint limits on walking will move the real figure. If walking itself is the issue, read the knee and back pages before you chase a smaller BMR.
Re-run the form when weight has changed by several kilograms, not after every dinner. The equation is linear in weight, so the output will move, but daily water weight is not a new metabolism. Pair any planned intake change with plates from the foods list so the math has something to land on.
If you arrived from a search for “BMR calculator” and you already know your BMI, you still need activity before you plan a day of food. Click through to the calorie tool rather than multiplying in your head and losing the activity table we publish there.