Calorie & TDEE Calculator

You're trying to lose 15 pounds and the internet keeps telling you to "just eat in a deficit" without any specific number to actually aim at. TDEE — Total Daily Energy Expenditure — is the calorie figure where your body burns exactly what you eat. Below it, you lose; above it, you gain. The trick is estimating it well enough to be useful.

The calculator uses Mifflin-St Jeor for BMR (body's resting calorie burn) and applies an activity multiplier from sedentary (1.2x) to extremely active (1.9x). Most people overestimate their activity level by a tier or two, so if you're not literally a tradesperson on your feet eight hours a day, sedentary or lightly active is probably accurate. The output is a starting estimate; track your weight for two weeks and adjust based on what actually happens.

The Mifflin-St Jeor formula: for men, BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5. For women, the constant is −161 instead of +5. The formula was derived in 1990 from indirect calorimetry measurements on a large sample, and it's been the dietitian default since. Activity multipliers: 1.2 (sedentary, desk job, no exercise), 1.375 (light exercise 1-3 days/week), 1.55 (moderate, 3-5 days), 1.725 (heavy, 6-7 days), 1.9 (extra heavy, hard physical job plus training). Multiply BMR by your honest multiplier and that's your TDEE.

A worked example: 35-year-old man, 180 cm tall, 85 kg, exercises 3-4 days a week. BMR: 10×85 + 6.25×180 − 5×35 + 5 = 850 + 1,125 − 175 + 5 = 1,805. Activity multiplier 1.55 (moderate): 1,805 × 1.55 = 2,797 calories per day for maintenance. To lose 1 pound per week (about 0.45 kg), you need a 500 cal/day deficit, so target around 2,300 calories. If after two weeks the scale hasn't moved, your real TDEE is lower than estimated — eat 200 fewer calories per day and reassess.

Where TDEE estimates fall apart: NEAT (non-exercise activity thermogenesis) varies wildly between people and within the same person across days. Some people fidget hundreds of calories away unconsciously; others are remarkably still. Adaptive thermogenesis kicks in during prolonged dieting — your body downregulates BMR by 5-15% to defend against weight loss, which is why the same deficit stops working after several months. The formula doesn't account for body composition either; lean mass burns more at rest than fat mass, so two people of the same weight can have measurably different real BMRs. Use the calculator as a starting estimate, weigh yourself daily and average over the week, and adjust calories every 2-3 weeks based on actual scale movement. The truth comes from the trend line, not the formula.