BMR Calculator
Calculate your Basal Metabolic Rate using multiple scientific formulas
Calculate with BMR Calculator
Your BMR Results
How to interpret this result
This is a middle-range resting-energy estimate for many adults; activity choice usually drives the larger planning change.
The formulas differ by about 54 calories/day here. Treat that spread as normal estimate uncertainty, not a measurement error.
BMR estimates resting calories only. Multiply by an activity factor for TDEE.
Formula Comparison
TDEE by Activity Level
Based on Mifflin-St Jeor BMR (1618 cal)
| Activity | Factor | TDEE |
|---|---|---|
Sedentary Little or no exercise | x1.2 | 1941 |
Light Exercise 1-3 days/week | x1.375 | 2224 |
Moderate Exercise 3-5 days/week | x1.55 | 2507 |
Active Exercise 6-7 days/week | x1.725 | 2790 |
Very Active Hard exercise daily | x1.9 | 3073 |
Practical Planning Output
Use as a first 1-2 week logging target.
A modest planning cut, not a medical target.
A small buffer for muscle-gain phases.
Use BMR as the resting baseline, then compare with the Calorie Calculator for goal targets, the Macro Calculator for food planning, or the Body Fat Calculator if you want to try a lean-mass equation.
Your result
Method, context, and limits
Use these notes to understand what the estimate is based on, when it helps, and where it can drift.
BMR equations estimate resting energy from age, sex, height, and weight rather than from a lab test.
Use BMR when you want the non-activity baseline that later feeds calorie, TDEE, or macro planning.
Real resting expenditure still shifts with lean mass, illness, medication, and recent weight change.
Health use guide
Estimates the calories your body uses at rest so you can build a more realistic daily intake plan from a clear baseline.
About This Tool
What is Basal Metabolic Rate and Why It Matters
Basal Metabolic Rate (BMR) is an estimate of the energy your body uses at rest for basic functions such as circulation, breathing, organ function, and temperature regulation. It is a starting point for energy planning because activity, exercise, digestion, and daily movement are added on top of resting needs. This calculator uses age, sex, height, weight, and optional body fat percentage to estimate BMR, then shows how the number changes under several activity assumptions. Treat the result as an educational estimate, not as a measured metabolic rate or medical nutrition plan.
BMR Calculation Formulas: Mifflin-St Jeor vs Harris-Benedict
This calculator implements three commonly used BMR and resting-energy prediction equations. The Mifflin-St Jeor equation, published in 1990, estimates resting energy expenditure from weight, height, age, and sex: men = 10 x weight(kg) + 6.25 x height(cm) - 5 x age + 5, women = 10 x weight(kg) + 6.25 x height(cm) - 5 x age - 161. The revised Harris-Benedict equation from 1984 uses different coefficients: men = 88.362 + 13.397 x weight + 4.799 x height - 5.677 x age, women = 447.593 + 9.247 x weight + 3.098 x height - 4.330 x age. These equations are educational estimates for planning, not diagnostic measurements of metabolism. If your activity, body composition, or health context is unusual, compare the formula spread and use observed weight and energy trends to adjust.
Katch-McArdle Formula for Body Composition Accuracy
The Katch-McArdle formula estimates BMR from lean body mass rather than total body weight: BMR = 370 + 21.6 x lean mass(kg). It can be useful when body fat percentage is known or reasonably estimated, especially when body composition differs from the assumptions behind weight-based formulas. The quality of the result depends heavily on the body fat input, so use it as another comparison scenario rather than a precise measurement. The Body Fat Calculator can provide a circumference-based estimate, while clinical tools such as DEXA or professional assessment may be used when precision matters.
Converting BMR to Daily Calorie Needs
BMR alone represents calories burned at complete rest, but actual daily needs depend on physical activity levels. To estimate Total Daily Energy Expenditure (TDEE), multiply BMR by an activity factor: sedentary (1.2) for minimal movement, lightly active (1.375) for light exercise one to three times weekly, moderately active (1.55) for moderate exercise three to five times weekly, very active (1.725) for intense exercise six to seven times weekly, and extra active (1.9) for demanding training or occupations. Additional factors include the thermic effect of food, non-exercise activity from daily movement, sleep, stress, and day-to-day variation. Use our TDEE Calculator for complete daily energy estimation, our Calorie Calculator for goal-based targets, and our Fiber Calculator to keep food planning tied to varied, fiber-containing foods instead of calories alone.
Limitations and Safe Interpretation
Formula-based BMR estimates cannot account for all differences in body composition, medications, thyroid conditions, pregnancy, recovery from illness, adaptive metabolic changes, or clinical nutrition needs. Compare the formula spread, choose an activity assumption that matches an average week, and adjust only after observing trends over time. If weight change, appetite, fatigue, lab results, or medical conditions are part of the question, use the calculator as background information and seek qualified guidance.
References & Sources
Common result checks
Questions about this tool
- What does BMR estimate?
- BMR estimates resting energy use from inputs such as age, sex, height, weight, and optionally body fat percentage. It is an educational estimate, not a measured metabolic test.
- Which BMR formula should I use?
- Mifflin-St Jeor is a common starting point. Harris-Benedict provides a comparison, and Katch-McArdle can be useful when you have a reasonable body fat estimate because it uses lean mass.
- How do I turn BMR into daily calories?
- BMR is resting energy only. Multiply it by an activity factor or use a TDEE or calorie calculator to estimate total daily energy needs from movement and exercise assumptions.
- Is this BMR calculator medical guidance?
- No. It provides educational estimates only. Medical conditions, medications, pregnancy, eating-disorder risk, and clinical nutrition needs should be reviewed with qualified health professionals.