Formulas estimate resting calorie burn within about 10%
High confidence
Resting metabolic rate is the calories your body burns just to stay alive at rest. A few simple formulas estimate it within about 10 percent for most healthy adults. They lose accuracy for people who are very lean or carrying a lot of extra weight.
Why it works
Most of the energy your body burns at rest comes from lean tissue — muscle and organs — not fat. The formulas estimate that lean tissue from four things you can measure: height, weight, age, and sex. From there they predict the calories it burns. Inside those cells, the mitochondria (the parts that turn fuel into energy) burn at a steady rate. So resting burn tracks closely with how much lean tissue you carry.
The evidence
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This retrospective study compared basal metabolic rate (the calories the body burns at rest) across 133 overweight and obese adults using indirect calorimetry (breath-based measurement), bioelectrical impedance, and two prediction equations. Measured BMR by indirect calorimetry averaged 1,581 kcal/day, which was significantly lower than the 1,766 kcal/day estimated by bioelectrical impedance. Of the equations tested, the Mifflin-St Jeor formula tracked the measured values most closely in this population.
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The authors built and tested a revised Harris-Benedict equation for estimating resting metabolic rate using data from 722 adults (173 men, 549 women). The new equations fit the measured data far better than the century-old original, with R-squared values of 0.95 for men and 0.86 for women versus 0.64 and 0.36 for the original. Predictions landed within 10% of measured rate for 67.5% of men and 59.1% of women, and the revised formulas had lower average error than both the original Harris-Benedict and the Mifflin-St Jeor equations.
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This study tested how well eight common equations predicted resting metabolic rate against breath-based indirect calorimetry in 30 healthy adults aged 18 to 65 with body mass index from 19 to 39. At the group level the Harris-Benedict and World Health Organization equations were most accurate, with small average bias of -14 and -25 kcal/day. But none of the equations worked reliably for individuals, and the error grew larger as a person's fat-free mass (muscle and organ mass) increased, with the equations underestimating rate in leaner, more muscular people.
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This study tested how well resting-energy-expenditure equations held up in overweight and obese class I and II adults (body mass index 25 to 40) in separate US and Dutch samples. In the US group the Mifflin-St Jeor equation was the most accurate, predicting within 10% of measured value for 79% of people with almost no average bias (-1.0%). In the Dutch group no equation reached that level of accuracy, so the study concluded there was no reliably accurate equation for Dutch overweight and obese adults.
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This is the landmark paper that created the Mifflin-St Jeor equation, still one of the most widely used ways to estimate resting calorie burn. Researchers measured resting energy expenditure by indirect calorimetry in 498 healthy adults (247 women, 251 men, ages 19 to 78), including both normal-weight and obese people, then used regression to link it to weight, height, age, and sex. The resulting equation explained 71% of the variation in resting energy (R-squared 0.71): 10 x weight in kg plus 6.25 x height in cm minus 5 x age in years, plus 5 for men or minus 161 for women.
Why we call confidence high
Multiple cross-validation studies point to the same result: Mifflin-St Jeor is the most accurate general-purpose formula, and it beats older equations across diverse populations.
Where it applies
Healthy adults
Last reviewed May 25, 2026. See how we score.