Estimate adult resting energy and an activity-adjusted daily value with Mifflin-St Jeor, or algebraically solve the equation for the weight implied by an entered resting-energy value.
Mifflin St Jeor Formula
The Mifflin-St Jeor equation predicts adult resting energy expenditure. “BMR” is a familiar calculator label, but this output is an equation estimate rather than a measured basal metabolic rate.
BMR (male) = 10*W + 6.25*H - 5*A + 5
BMR (female) = 10*W + 6.25*H - 5*A - 161
To estimate total daily energy expenditure (TDEE), the calories you burn in a full day including activity, multiply your BMR by an activity factor.
TDEE = BMR * activity factor
- W = body weight in kilograms (kg)
- H = height in centimeters (cm)
- A = age in years
- activity factor = a multiplier from 1.2 (sedentary) to 1.9 (extra active)
The formula uses weight, height, age, and the equation’s sex constant to predict a group-average resting value. The selected activity factor then creates a rough daily estimate; it does not measure an individual’s total energy expenditure.
If you enter US units, pounds are converted to kilograms with 0.45359237 and inches to centimeters with 2.54. In reverse mode, the calculator solves the resting equation directly for body weight from the entered target resting value. It does not divide a calorie-intake goal by an activity factor, and the implied weight is not a healthy-weight recommendation.
Activity Multipliers and Calorie Targets
The activity factor you choose has a large effect on your TDEE. Pick the level that matches a normal week, not your best week.
| Activity level | Description | Factor |
|---|---|---|
| Sedentary | Little or no exercise, desk job | 1.2 |
| Lightly active | Light exercise 1-3 days/week | 1.375 |
| Moderately active | Moderate exercise 3-5 days/week | 1.55 |
| Very active | Hard exercise 6-7 days/week | 1.725 |
| Extra active | Physical job or twice-daily training | 1.9 |
The calculator can add or subtract a fixed planning amount from the activity-adjusted estimate. This arithmetic does not predict a specific rate of weight change or establish a safe intake.
| Planning option | Arithmetic | Interpretation |
|---|---|---|
| Below estimate | TDEE estimate minus 250 or 500 | Planning value only; not a predicted loss rate |
| No adjustment | TDEE estimate | Equation-based maintenance starting estimate |
| Above estimate | TDEE estimate plus 250 or 500 | Planning value only; not a predicted gain rate |
Example Problems
Example 1. A 30-year-old male weighs 80 kg and is 180 cm tall, with a moderately active lifestyle.
BMR = 10(80) + 6.25(180) - 5(30) + 5 = 800 + 1125 - 150 + 5 = 1780 calories per day.
TDEE = 1780 * 1.55 = 2759 calories per day.
Example 2. A 25-year-old female weighs 60 kg and is 165 cm tall, with a lightly active lifestyle.
BMR = 10(60) + 6.25(165) - 5(25) - 161 = 600 + 1031.25 - 125 - 161 = 1345.25 calories per day.
TDEE = 1345.25 * 1.375 = 1850 calories per day.
FAQ
What is the difference between BMR and TDEE?
With the listed activity multipliers above 1, estimated TDEE is numerically higher than the resting estimate. It is a planning starting point, not a prescribed intake.
Why is the Mifflin-St Jeor equation recommended?
The 1990 equation was derived against measured resting energy expenditure in 498 healthy adults ages 19–78. Predictive accuracy varies by person and population; indirect calorimetry measures resting expenditure more directly.
How accurate is the result for me?
The equation does not measure metabolism directly and does not include body composition. Treat it as a starting estimate, not a minimum intake or prescription. Pregnancy, breastfeeding, eating-disorder history, illness, and weight-affecting medication require individualized guidance.
