How Many Calories Do I Need Each Day?
BMR, activity multipliers and how to turn a maintenance number into a weight-loss or muscle-gain target.
5 min read
Step by step
- Estimate BMR with the Mifflin-St Jeor equation from weight, height, age and sex.
- Multiply by an activity factor from 1.2 (sedentary) to 1.9 (athlete) to get TDEE.
- Eat at TDEE to maintain, about 500 kcal below to lose, 250–500 above to gain.
- Recalculate every few months as your weight changes.
Key takeaway: Maintenance calories = BMR × activity factor.
BMR: the idling speed of your body
Your basal metabolic rate is the energy you burn at complete rest. The Mifflin-St Jeor equation estimates it from weight, height, age and sex, and is the formula most often recommended by dietetic associations for healthy adults.
For a 30-year-old, 75 kg, 175 cm man: BMR = 10 × 75 + 6.25 × 175 − 5 × 30 + 5 ≈ 1,699 kcal per day before any activity.
From BMR to TDEE
Total daily energy expenditure multiplies BMR by an activity factor: 1.2 sedentary, 1.375 light, 1.55 moderate, 1.725 very active, 1.9 athlete. The example above at moderate activity needs about 2,633 kcal per day to maintain weight.
Be honest with the activity multiplier — most people with desk jobs and a few weekly workouts are 'light', not 'moderate'. Overestimating activity is the most common reason calorie targets fail.
Adjusting for goals
A deficit of about 500 kcal per day corresponds to roughly 0.5 kg of fat loss per week; a surplus of 250–500 kcal supports gradual muscle gain. Avoid deficits below about 1,200 kcal (women) or 1,500 kcal (men) without medical supervision.
Recalculate every few months: as your weight changes, so does your maintenance number.
Do it automatically
Daily maintenance calories and BMR using the Mifflin-St Jeor equation.
Open the Calorie Calculator