BMR & TDEE Calculator
Enter your sex, age, height, weight, and activity level to calculate your Basal Metabolic Rate (BMR) and Total Daily Energy Expenditure (TDEE). Results use the Mifflin-St Jeor equation with the Harris-Benedict (1984 revision) shown for reference.
Sex
Activity level
This tool provides estimates based on published formulas and is not medical or dietary advice. Actual calorie expenditure varies widely due to individual body composition, health conditions, and metabolic factors. Consult a healthcare professional or registered dietitian before making significant changes to your diet. Not intended for people under 18, pregnant or breastfeeding individuals, or those with medical conditions.
How to use
Enter your sex, age, height, and weight — BMR appears instantly. Select an activity level to see your TDEE and calorie targets for weight loss, maintenance, and lean bulk. Toggle between metric (cm/kg) and imperial (ft/lbs); existing values convert automatically.
Two practical use cases: First, before a first session with a personal trainer — the four inputs (weight, height, age, activity) are exactly what trainers ask first, so knowing your BMR and TDEE in advance makes the conversation about calorie targets faster and more productive. Second, when setting a calorie goal in a fitness app like MyFitnessPal or Cronometer — paste this tool's TDEE as your 'maintenance' baseline and let the app calculate a deficit or surplus from there.
How the formulas work
This tool uses two equations. The primary one is the Mifflin-St Jeor equation (1990): Male BMR = 10 × weight[kg] + 6.25 × height[cm] − 5 × age + 5; Female BMR = 10 × weight[kg] + 6.25 × height[cm] − 5 × age − 161. A 2005 comparison study (Frankenfield et al.) found Mifflin-St Jeor to be the most accurate predictive equation for both non-obese and obese adults and is now the standard recommended by nutrition researchers and clinicians.
The reference value uses the Harris-Benedict equation (1984 revision by Roza & Shizgal): Male BMR = 88.362 + 13.397 × weight + 4.799 × height − 5.677 × age; Female BMR = 447.593 + 9.247 × weight + 3.098 × height − 4.330 × age. Originally published in 1919, it remained the standard for over 70 years. Why does this tool show both? Because seeing the difference — for a 30-year-old male, 175 cm, 70 kg, Mifflin gives 1,648 kcal vs Harris-Benedict 1,695 kcal — illustrates that BMR estimates carry an inherent margin. Harris-Benedict tends to run slightly higher for men; the gap is smaller for women. When the two formulas agree closely, you can have more confidence in the estimate.
TDEE = BMR × activity factor. The five activity factors (1.2 to 1.9) originate from McArdle et al.'s Exercise Physiology (1996) and are widely used as an industry standard. A common mistake: if you exercise three times a week but sit at a desk for eight hours otherwise, 'Moderately active' (×1.55) is likely an overestimate — 'Lightly active' (×1.375) is often more accurate. Overestimating your activity level is the single biggest reason why calorie math 'looks right on paper' but doesn't translate to real results.
Frequently asked questions
- What's the difference between BMR and TDEE?
- BMR (Basal Metabolic Rate) is the energy your body burns at complete rest — breathing, heartbeat, keeping warm, organ function. It's what you'd burn if you stayed in bed all day. TDEE (Total Daily Energy Expenditure) adds on top of that everything you do: walking, working, exercising. To lose weight, your calorie intake needs to be below your TDEE, not just your BMR. Eating below your BMR consistently suppresses your metabolism and tends to backfire over time.
- How do I pick the right activity level?
- When in doubt, go one step lower than you think. Research consistently shows people overestimate how active they are. 'Walk 30 minutes a day, desk job otherwise' → Lightly active (×1.375). 'Gym 5 days a week plus a desk job' → Moderately active (×1.55) at most. 'Construction worker or athlete training twice a day' → Very active or Extra active. The most common mistake is choosing Moderately active when the reality is light exercise on top of 8+ hours of sitting. One step lower still gives you room to adjust upward once you've tracked your actual intake and weight trend for a few weeks.
- Why does this tool show two formulas?
- To give you a sense of the estimation range. Mifflin-St Jeor (1990) is the most accurate for most adults based on current research. Harris-Benedict (1984 revision) is a classic formula that's been used for decades. For most people they're within 50–100 kcal of each other. When they agree closely, the estimate is more reliable. When they diverge significantly, it's a reminder that BMR formulas are population-level estimates with individual variation — not precise measurements.
- I'm eating less than my BMR but not losing weight. Why?
- A few common reasons: (1) Metabolic adaptation — your body adjusts its metabolic rate down in response to sustained restriction, a well-documented process. (2) Food tracking errors — research shows people under-report intake by 20–40% on average, often unintentionally. (3) The formula is an estimate — individual BMR can vary ±10–15% from any prediction. Rather than chasing the exact number, focus on a multi-week trend: weigh yourself at the same time each morning and look at the weekly average. That gives you real data to adjust from.