BMR & TDEE Calculator: Mifflin–St Jeor Basal Metabolic Rate and Daily Energy Expenditure
Free online BMR (Basal Metabolic Rate) and TDEE (Total Daily Energy Expenditure) calculator. It estimates daily calories from your sex, height, weight, age and one of five activity factors (1.2–1.9), using the Mifflin–St Jeor equation with a Harris–Benedict comparison shown side by side. Results update live and can be saved to local history, with all calculations running privately in your browser.
Personal details & activity
Basal metabolism via the Mifflin–St Jeor equation
Metabolism & energy expenditure
BMR at rest · TDEE total daily burn
The Mifflin–St Jeor equation is recommended by the Academy of Nutrition and Dietetics as the most accurate BMR formula: men 10w+6.25h−5a+5, women 10w+6.25h−5a−161. TDEE multiplies BMR by an activity factor.
How to Use
Basal Metabolic Rate & TDEE Guide
Mifflin–St Jeor equation · activity factors
BMR (Basal Metabolic Rate) is the minimum energy your body needs at complete rest to keep the heart beating, lungs breathing and temperature stable. TDEE (Total Daily Energy Expenditure) multiplies BMR by an activity factor and represents the calories you actually burn in a day. FinCompute uses the Mifflin–St Jeor equation recommended by the Academy of Nutrition and Dietetics, shows the classic Harris–Benedict result for reference, and applies five activity levels — the starting point for fat loss, muscle gain or maintenance.
01 Choosing a BMR equation
The Mifflin–St Jeor equation (1990) has the smallest error in modern populations and is the preferred choice: men BMR = 10w + 6.25h − 5a + 5, women BMR = 10w + 6.25h − 5a − 161, where w is kg, h is cm and a is age.
The Harris–Benedict equation (1918, revised 1984) is older and typically gives a value about 5% higher; we show it for comparison. Both are population estimates — your true BMR varies with body composition, thyroid function, genetics, hormones and medications, typically within ±10%.
- Sedentary (desk job, little exercise): ×1.2
- Lightly active (exercise 1–3 days/week): ×1.375
- Moderately active (exercise 3–5 days/week): ×1.55
- Very active (hard exercise 6–7 days/week): ×1.725
- Extra active (physical job or athlete): ×1.9
02 Using TDEE to set your intake
For fat loss, a daily deficit of 300–500 kcal (≈0.3–0.5 kg/week) is common; for muscle gain a surplus of 250–500 kcal/day works. Intake should not drop below BMR for long, as very-low-calorie diets lower metabolism, cost muscle and raise rebound risk. Women are generally advised not to go below 1200 kcal/day or men below 1500 kcal/day, with adequate protein.
Inputs
- Metric / ImperialSwitches between cm/kg and ft-in/lb input fields.
- sexSelects male or female BMR formula constants.
- ageYour age in years.
- heightYour height (cm or ft/in).
- weightYour weight (kg or lb).
- activity levelFive levels from sedentary (×1.2) to extra active (×1.9) applied to BMR for TDEE.
Actions
- CalculateBMR and TDEE update live as you type; this button saves the result to the history drawer.
- ResetRestores the default inputs.
- As you lose weight, BMR and TDEE drop — recalculate every 3–5 kg
- Strength training preserves muscle and limits the metabolic slowdown during fat loss
- Poor sleep lowers TDEE and increases appetite; aim for 7–9 hours on a cut
- A fitness tracker or indirect calorimetry can give you a more personal estimate
- These results are for healthy adults; pregnant, breastfeeding or ill people should consult a dietitian
BMR (Basal Metabolic Rate) is the minimum energy your body needs at rest, while TDEE (Total Daily Energy Expenditure) adds daily activity. This calculator uses the Mifflin–St Jeor equation recommended by the Academy of Nutrition and Dietetics, with a Harris–Benedict comparison, estimating daily calories from sex, height, weight, age and one of five activity factors.
The Mifflin–St Jeor equation
Men: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5. Women: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161. Published in 1990, it was rated by the Academy of Nutrition and Dietetics as more accurate than the older Harris–Benedict equation.
TDEE = BMR × activity factor
Sedentary ×1.2 (desk job, little exercise); lightly active ×1.375 (light exercise 1–3 days/week); moderately active ×1.55 (moderate exercise 3–5 days/week); very active ×1.725 (hard exercise 6–7 days/week); extra active ×1.9 (physical job or daily hard training).
BMR vs TDEE
BMR is what you burn lying still to sustain breathing, heartbeat and temperature; TDEE includes work, walking, exercise and the thermic effect of food. Set fat-loss or muscle-gain intake against TDEE, but avoid eating below BMR for long periods to prevent metabolic adaptation and muscle loss.
Using the results for weight management
For fat loss, create a 300–500 kcal daily deficit from TDEE; for muscle gain, a 200–400 kcal surplus; to maintain, eat near TDEE. Pair this with the Calorie Target and Macronutrient calculators to turn the target into daily grams.
FAQ
QHow is Mifflin–St Jeor calculated?
Men BMR = 10w + 6.25h − 5a + 5; women = 10w + 6.25h − 5a − 161 (w kg, h cm, a years). TDEE = BMR × activity factor.
QWhat is the difference between BMR and TDEE?
BMR is energy burned at complete rest; TDEE includes daily activity and exercise. Set intake against TDEE but do not eat below BMR for long.
QWhich activity factor should I choose?
Sedentary 1.2 for a desk job; 1.375 for light exercise 1–3 days; 1.55 for 3–5 moderate days; 1.725 for 6–7 hard days; 1.9 for a physical job or twice-daily training.
QWhy are there two BMR results?
The tool shows both the newer, more accurate Mifflin–St Jeor (1990) and the classic Harris–Benedict revision (1984); they usually differ by tens to ~100 kcal, so use the main value as a guide.
QDoes metabolism change as my weight changes?
Yes — BMR generally drops as you lose weight (there is less of you), which contributes to fat-loss plateaus. Recalculate TDEE every 3–5 kg of weight change.