BMR & TDEE Calculator
This tool estimates your Basal Metabolic Rate (BMR) and Total Daily Energy Expenditure (TDEE) from your sex, age, height, and weight using the Mifflin-St Jeor equation, then scales BMR by an activity factor to reflect how much you move.
How the estimate works
The Mifflin-St Jeor equation, published in 1990, predicts BMR — the energy your body uses at complete rest — from four inputs: BMR (kcal/day) = 10 × weight(kg) + 6.25 × height(cm) − 5 × age(years) + s, where s is +5 for men and −161 for women. To reach TDEE, the calculator multiplies that BMR by an activity factor that stands in for your typical movement: 1.2 (sedentary), 1.375 (light activity), 1.55 (moderate), 1.725 (active), or 1.9 (very active). TDEE is always higher than BMR because it adds the energy spent on movement, exercise, and digesting food.
These figures are statistical estimates. The equation was fitted to a study of healthy adults, so it describes a population average rather than your exact metabolism, and the activity multipliers are broad self-reported bands. It does not account for body composition (muscle burns more energy than fat), pregnancy, illness, thyroid or other medical conditions, medications, or very high or low body sizes. Independent studies find Mifflin-St Jeor lands within about 10% of measured metabolic rate in roughly 82% of healthy people — which also means individual results commonly differ by 10% or more.
Treat the output as a starting point to refine over time, not a prescription. This tool does not provide medical advice or a diagnosis. If you are pregnant or breastfeeding, managing a health condition, taking medication that affects metabolism, an athlete with high muscle mass, or planning a significant change in weight, confirm your calorie targets with a doctor or a registered dietitian before acting on the number.
Frequently asked questions
What is the difference between BMR and TDEE?
BMR (Basal Metabolic Rate) is the energy your body uses at complete rest just to keep your organs running. TDEE (Total Daily Energy Expenditure) is your whole-day burn — BMR plus the calories used for movement, exercise, and digesting food. Because TDEE adds activity on top of BMR, it is always the larger of the two numbers.
Why does this calculator use the Mifflin-St Jeor equation?
In validation studies that compared common prediction formulas against metabolic rate measured by indirect calorimetry, Mifflin-St Jeor was the most accurate for the general population, landing within 10% of the measured value in about 82% of healthy adults. For that reason it has largely replaced the older Harris-Benedict equation from 1919 in dietetic practice.
How accurate is the result?
It is an estimate, not a measurement. Even the best-performing equation carries individual error, and factors such as muscle mass, hormones, and how honestly activity level is reported all shift the true figure. The only precise way to measure BMR is indirect calorimetry in a clinical setting. Use the output as a reasonable ballpark and adjust based on how your body actually responds.
Can I use this to lose or gain weight?
TDEE is a sensible reference point: eating consistently below it tends to produce weight loss and above it weight gain. But this tool only estimates energy needs — it is not a diet plan and offers no medical advice. For a safe, personalized target, particularly if you have a health condition or are pregnant, speak with a doctor or registered dietitian.
