Calculate your Basal Metabolic Rate — the calories your body burns at complete rest.
Basal Metabolic Rate (BMR) represents the absolute baseline of human energy expenditure — the number of calories your body burns simply to keep you alive while completely at rest, powering essential functions like breathing, blood circulation, cell repair, and brain activity, before accounting for any movement or digestion at all. The CalcEqual BMR Calculator computes this figure using two well-established predictive equations side by side — the modern Mifflin-St Jeor formula and the classic Harris-Benedict formula — so you can compare both estimates.
BMR serves as the essential building block underlying virtually every calorie-related calculation in nutrition science: TDEE, weight loss targets, and macronutrient planning all start from a BMR estimate as their foundation. Understanding your own approximate BMR helps explain why two people of similar weight can have noticeably different calorie needs — BMR is influenced by body composition, age, sex, and genetics, not just total body weight.
This calculator deliberately shows two different formulas rather than just one, since comparing the Mifflin-St Jeor and Harris-Benedict results provides a useful sanity-check range — when both formulas produce similar figures (as they typically do), you can be more confident in the estimate; larger discrepancies between the two can occur at unusual height-weight combinations, which is itself informative.
Importantly, BMR is not something you should attempt to eat below for weight loss purposes — doing so risks muscle loss, metabolic slowdown, and nutrient deficiencies, since BMR represents calories needed merely to sustain basic life functions, not a discretionary number that can be safely reduced.
Some clinical settings use indirect calorimetry — directly measuring oxygen consumption and carbon dioxide production through specialized breathing equipment — to obtain a measured BMR rather than relying on predictive equations, though this approach requires specialized equipment not available outside research or clinical settings, which is why predictive formulas like Mifflin-St Jeor remain the practical standard for everyday use.
The original Harris-Benedict equation was published in 1919 based on data from indirect calorimetry studies — a genuinely pioneering effort for its time, but one that researchers later found systematically overestimated BMR for the modern population, partly reflecting changes in average body composition and lifestyle since the early 20th century. A 1984 revision adjusted the original coefficients, and the equation remained the dominant clinical standard for decades afterward.
The Mifflin-St Jeor equation, published in 1990, was developed using a larger and more contemporary dataset, and subsequent validation research — including a influential 2005 review published in the Journal of the American Dietetic Association — found it to be more accurate for the general population than Harris-Benedict, leading most modern nutrition guidelines to recommend it as the preferred formula today.
Approximate BMR by age group for a 170 lb, 5'10" male (Mifflin-St Jeor):
| Age | Approx. BMR |
|---|---|
| 20 | 1,837 kcal |
| 30 | 1,737 kcal |
| 40 | 1,637 kcal |
| 50 | 1,537 kcal |
| 60 | 1,437 kcal |