TDEE / Calorie Calculator
Calculate Total Daily Energy Expenditure (TDEE) — your daily calorie need to maintain weight — plus targets for fat loss, lean gain, and aggressive cutting. Uses the Mifflin-St Jeor equation.
How to Use
- Enter your sex (used by the Mifflin-St Jeor equation).
- Enter your age, weight (kg), and height (cm).
- Pick your activity level — be honest. Most people overestimate.
- Read your maintenance calories (TDEE) and goal-specific targets: cut, lean cut, lean bulk, bulk.
- Use the macro split as a starting point, not a strict prescription. Adjust based on how you respond.
- Re-run every 4–6 weeks as your weight changes — TDEE shifts with body mass.
Formulas
A Brief History of Calorie Counting
The calorie as a unit of food energy was popularized in the United States by Wilbur Atwater, a USDA chemist, in the 1890s. Atwater's bomb calorimeter measured the heat released by burning food samples; his Atwater system (4 kcal/g for protein and carbs, 9 kcal/g for fat, 7 kcal/g for alcohol) is still the basis of modern food labels. Calorie counting as a popular weight-loss strategy traces to Lulu Hunt Peters' 1918 bestseller Diet and Health: With Key to the Calories and has waxed and waned in fashion ever since.
The Harris-Benedict equation (1919, revised 1984) was the standard BMR estimate for most of the 20th century. The Mifflin-St Jeor equation (1990) replaced it as the recommended default after large-scale validation studies showed it more accurately predicted measured BMR in modern populations. Both are derived from the same kind of indirect-calorimetry measurements but with different age and activity demographics in their training data.
Modern understanding has complicated the simple "calories in, calories out" model with concepts like adaptive thermogenesis, NEAT (non-exercise activity thermogenesis), and the differential effects of macronutrient composition on satiety and metabolism. The first law of thermodynamics still holds — but the body's response to a given calorie deficit isn't a simple linear function of its size. Modern coaching emphasizes consistency, sustainable deficits, and adjusting based on real-world results rather than slavish adherence to formula output.
About This Calculator
This calculator uses the Mifflin-St Jeor equation for BMR and the standard activity multipliers (1.2 sedentary through 1.9 very active) to estimate TDEE. Goal-specific targets are computed from TDEE with conservative deficits/surpluses sized for ~0.5–1% body weight change per week — the range that minimizes muscle loss during a cut and fat gain during a bulk.
This is informational, not medical advice. Caloric needs vary individually by genetics, body composition, training history, sleep quality, and many other factors the formula can't capture. Track your weight weekly and adjust the calorie target empirically rather than trusting any formula over results. Consult a qualified clinician or dietitian for personalized guidance, especially with medical conditions or pregnancy. Everything runs entirely in your browser; no health data is transmitted or stored.
Frequently Asked Questions
What is TDEE?
Total Daily Energy Expenditure — the total calories your body burns in 24 hours, including basal metabolism (BMR), digestion (TEF, ~10%), exercise activity (EAT), and non-exercise movement (NEAT). TDEE = BMR × activity factor approximates this. To maintain weight, eat at TDEE; to lose, eat below; to gain, eat above.
Which BMR equation does this use?
Mifflin-St Jeor (1990), the most accurate equation for the general modern population per multiple validation studies. The older Harris-Benedict (1919, revised 1984) tends to overestimate by 5%. Katch-McArdle is slightly better if you know your body-fat percentage but not most people do. For practical purposes Mifflin-St Jeor is the right default.
How accurate are the activity multipliers?
They're rough — typical real-world variation per multiplier is ±10–15%. The biggest source of error is people overestimating their activity level. 'Sedentary' applies to most desk workers who aren't deliberately exercising. 'Light' is for people training 2–3 days per week or with active jobs. 'Very active' is for genuine athletes or laborers. If your weight isn't moving as expected after 2–3 weeks, adjust — don't trust the formula over your scale.
How fast should I lose weight?
Sustainable fat loss is around 0.5–1% of body weight per week. For a 180 lb person, that's 1–2 lb/week, which means a 500–1,000 calorie/day deficit. Faster loss tends to lose more muscle and is harder to maintain. The 'aggressive cut' target in the calculator is roughly the upper bound of safe sustained loss for most people.
Why do I plateau even though I'm eating below TDEE?
Several possibilities. (1) Adaptive thermogenesis — your body reduces NEAT and BMR as you lose weight. Recalculate TDEE with your new weight and the deficit may need adjustment. (2) Underestimating intake — most people undercount calories by 20–40%. Track precisely with a kitchen scale for two weeks. (3) Water and glycogen fluctuations mask fat loss; the trend over 4 weeks matters more than the daily scale.
Should I eat the same on rest days?
It's simpler to eat the same amount every day at the average. Calorie cycling (more on training days, less on rest days) can work for advanced trainees but adds complexity. For most people, a consistent daily intake is easier to track and the body uses calories on a multi-day rolling basis anyway.
Common Use Cases
Setting up a fat-loss diet
Calculate TDEE, subtract 300–500 calories, eat that target for 4 weeks, reassess based on actual weight change.
Lean bulking for muscle gain
Eat 200–300 calories above TDEE to build muscle while minimizing fat gain. Track weekly weight; aim for ~0.25–0.5% body weight per week.
Maintenance after a cut
Transition from a deficit to maintenance carefully — slowly add calories back over 2–3 weeks to avoid rapid rebound.
Recomposition
Eating very near maintenance with strength training can build muscle while losing fat, especially in beginners or those returning from a layoff.
Endurance training fueling
Athletes training 5+ hours per week often need much more than the standard activity multipliers suggest — track and adjust.
Reverse dieting
Slowly increase calories from a depressed metabolism to restore TDEE without immediate fat regain.
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