Daily Calorie Need

Total Daily Energy Expenditure (TDEE) is the total number of calories your body burns in a day. It combines your resting metabolic rate with your physical activity level.

Step 1. Calculate Basal Metabolic Rate (BMR) using the Mifflin-St Jeor equation:

For men: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5

For women: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161

Step 2. Multiply by an activity factor:

TDEE = BMR × Activity Factor

Activity factors:

• Sedentary (desk job, no exercise): × 1.2
• Lightly active (1–3 days/week exercise): × 1.375
• Moderately active (3–5 days/week): × 1.55
• Very active (6–7 days/week hard exercise): × 1.725
• Extremely active (physical job + hard training): × 1.9

Worked example: Male, 35 years old, 80 kg, 178 cm tall, moderately active.

BMR = (10 × 80) + (6.25 × 178) − (5 × 35) + 5 BMR = 800 + 1,112.5 − 175 + 5 = 1,742.5 calories/day TDEE = 1,742.5 × 1.55 = 2,701 calories/day

Calorie targets by goal:

• Lose weight (0.5 kg/week): TDEE − 500 calories/day
• Lose weight (1 kg/week): TDEE − 1,000 calories/day
• Maintain weight: TDEE
• Gain muscle (lean bulk): TDEE + 300–500 calories/day

Those deficits come from the rule that a kilogram of body fat stores roughly 7,700 calories, so 500 a day for a week is about half a kilo. It is a planning approximation rather than a law. Real loss slows as you get lighter, because a smaller body has a smaller BMR and the same TDEE figure stops applying. Recalculate every 5 kg or so.

Never eat below your BMR for extended periods. It costs muscle rather than fat, and it drives the metabolic adaptation that makes the next attempt harder. The practical floors are around 1,200 calories a day for women and 1,500 for men, and this calculator will tell you when a target it just printed falls below yours.

The activity factor is where almost all the error lives. BMR from Mifflin-St Jeor is good to about 10%. The multipliers are much rougher, and people reliably pick one step too high: a desk job plus two gym sessions is lightly active, not moderately. The gap between 1.375 and 1.55 on a 1,700 calorie BMR is nearly 300 calories a day, which is the entire difference between losing weight and not.

How to actually use the number. Eat at the maintenance figure for two or three weeks and weigh yourself at the same time each morning. If the average holds steady, your TDEE estimate was right and you can apply a deficit to it with confidence. If it drifts, adjust by 100 to 200 calories rather than starting over. That two-week calibration is worth more than any formula, because it measures you instead of predicting you.