Resting Energy Guide | EZ Calculators

Define the Resting-Energy Question Before Calculating

Basal metabolic rate describes energy measured under strict basal conditions. Resting metabolic rate or resting energy expenditure uses less restrictive rest conditions, while total daily energy expenditure adds movement, exercise, and food thermogenesis. These related quantities answer different questions.

Mifflin-St Jeor predicts resting energy from age, weight, height, and two published sex-coefficient groups. Although BMR is common search language, the output remains a regression estimate rather than a metabolic diagnosis, maintenance estimate, or food-intake instruction.

Prepare Inputs That Preserve the Physical Measurements

Use completed years, recent measured weight, and standing height. The equation expects kilograms and centimetres: 1 lb equals 0.45359237 kg and 1 in equals 2.54 cm. Preserve unrounded metric values until display.

Choose the male or female coefficient published by the equation. This binary model variable cannot describe every person's physiology or identity. Document the choice when it matters and seek a more suitable assessment rather than implying the equation knows inputs it never received.

Check that pounds were not entered in a kilogram field.
Use total inches, not a decimal such as 5.10 for 5 feet 10 inches.
Enter current measured weight instead of a goal weight.
Keep the same measurements when comparing equations.

Reconstruct Mifflin-St Jeor Component by Component

For the male coefficient, calculate 10 times kilograms plus 6.25 times centimetres minus 5 times age, then add 5. For the female coefficient, subtract 161 instead. The 1990 development study measured resting energy by indirect calorimetry in 498 healthy adults ages 19 through 78.

For 75 kg, 178 cm, age 30, and the male coefficient, the terms are 750 + 1,112.5 - 150 + 5. The unrounded estimate is 1,717.5 kcal/day. A transparent ledger makes input or unit errors visible and prevents a rounded display from being mistaken for the exact internal result.

Formula notes

Male coefficient: REE = 10W + 6.25H - 5A + 5.
Female coefficient: REE = 10W + 6.25H - 5A - 161.
Daily kilojoules = daily kilocalories x 4.184.

Use Revised Harris-Benedict as a Visible Cross-Check

Roza and Shizgal published revised Harris-Benedict coefficients in 1984. With the same 75 kg, 178 cm, age 30, and male coefficient, that equation predicts about 1,777.0 kcal/day. The difference from Mifflin-St Jeor is about 59.5 kcal/day, or roughly 3.5% of the Mifflin estimate.

The difference exposes method sensitivity; it is not a confidence interval or proof that either prediction is closer to one person's measured value. Validation results vary across body sizes, age groups, athletic populations, and health settings.

Formula notes

Revised Harris-Benedict male coefficient: 88.362 + 13.397W + 4.799H - 5.677A.
Revised Harris-Benedict female coefficient: 447.593 + 9.247W + 3.098H - 4.330A.

Interpret Coefficients Without Turning Them Into Personal Rules

With other inputs fixed, Mifflin adds 10 kcal/day per entered kilogram, 6.25 per centimetre, and subtracts 5 per year. These fitted regression coefficients do not predict how one person's measured metabolism will respond to weight change, aging, training, or altered body composition.

The form does not measure fat-free mass. Health, medication, hormones, pregnancy, lactation, sleep, recent food or exercise, temperature, and metabolic adaptation can affect measured energy without appearing in either equation.

Understand Prediction Error and Indirect Calorimetry

Correct code can still miss an individual's measured resting energy. Reviews often define accuracy as falling within 10% of indirect calorimetry, yet people still fall outside that band. Arithmetic correctness and biological prediction accuracy are separate claims.

Indirect calorimetry estimates expenditure from respiratory gases and is the reference when measurement matters clinically. Fasting, recent exercise, pretest rest, room conditions, calibration, and steady-state criteria still affect comparison with an equation.

Place Resting Energy Inside the Larger Energy Model

Resting energy is only one part of a day. TDEE also includes exercise, daily movement, posture, and food thermogenesis. An activity multiplier creates another estimate; it does not turn predicted resting energy into measured daily expenditure.

For planning, record the equation, inputs, activity method, adjustment, and observation period separately. Multi-week intake and weight trends may help calibration, while short-term weight also shifts with water, glycogen, sodium, digestion, and menstrual-cycle effects.

Use the BMR page for resting-energy arithmetic.
Use the TDEE page when activity must be included.
Use a dynamic model such as NIDDK's Body Weight Planner for time-based weight scenarios.
Use qualified nutrition care when the result could affect health or treatment.

Know When a General Adult BMR Calculator Is the Wrong Tool

Do not apply this general adult equation to children, pregnancy or breastfeeding, frailty, eating disorders, severe undernutrition, major recent weight change, hospitalization, critical illness, nutrition support, or unexplained symptoms. Athletes with unusual body composition may also need another method.

Never use a low result to justify severe restriction or a high result to dismiss unexpected weight change. A registered dietitian or qualified healthcare professional can assess whether another equation, indirect calorimetry, or evaluation is appropriate.

Seek care for unexplained weight change or symptoms instead of diagnosing metabolism online.
Use pediatric methods for anyone under 18.
Use prenatal or lactation guidance during pregnancy and breastfeeding.
Avoid repeated calculation when calorie or body tracking worsens anxiety or disordered eating.

Frequently asked questions

How do I calculate BMR with Mifflin-St Jeor?

Convert weight to kilograms and height to centimetres. Calculate 10 times weight plus 6.25 times height minus 5 times age, then add 5 for the published male coefficient or subtract 161 for the published female coefficient. The result predicts resting energy in kcal/day.

What is the difference between BMR and RMR?

Strict BMR is measured under more restrictive basal conditions, including fasting and complete rest after sleep. RMR or REE uses less restrictive resting conditions. Mifflin-St Jeor was developed to predict resting energy expenditure, although online calculators commonly call the result BMR.

What is the difference between BMR and TDEE?

BMR or predicted REE covers resting energy only. TDEE adds physical activity, non-exercise movement, and food thermogenesis. This page does not use an activity multiplier; use the separate TDEE Calculator for an activity-adjusted estimate.

Should I eat the number shown by a BMR calculator?

Not automatically. The result is a predicted resting-energy value, not a dietary prescription or minimum intake. Food needs depend on total expenditure, goals, health, life stage, and professional guidance. Severe restriction based only on BMR can be unsafe.

How accurate is the Mifflin-St Jeor equation for one person?

It is a population regression equation, not a direct measurement. Validation studies find useful average performance but meaningful individual over- and underprediction. Correct inputs and arithmetic do not guarantee that the estimate matches indirect calorimetry.

References

These sources support the method or guidance used for BMR Calculator. Verify time-sensitive rules at the source.

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Open BMR Calculator, enter your scenario, and compare its supporting rows with this guide's method and checks.

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