Calorie Calculator — Daily Calorie Needs (Mifflin-St Jeor)
Calculate your daily calorie needs using the Mifflin-St Jeor equation for weight loss, maintenance, or muscle gain. Includes activity level adjustments.
How Your Daily Calorie Needs Are Calculated
This calculator uses the Mifflin-St Jeor equation — the most widely validated formula for estimating resting energy expenditure in modern adult populations. It was first published in 1990 and has been shown in multiple studies to be more accurate than the older Harris-Benedict formula, particularly for overweight individuals.
Women: BMR = (10 × kg) + (6.25 × cm) − (5 × age) − 161
TDEE (Total Daily Calories) = BMR × Activity Multiplier
Understanding the Activity Multipliers
| Activity Level | Multiplier | What It Means |
|---|---|---|
| Sedentary | 1.2× | Desk job, little or no planned exercise |
| Lightly Active | 1.375× | Walking, light gym workouts 1–2 days/week |
| Moderately Active | 1.55× | Gym 3–5 days/week or physically active job |
| Very Active | 1.725× | Hard training 6–7 days/week |
| Extra Active | 1.9× | Twice-daily training or manual labor + exercise |
Calorie Targets for Different Goals
- Lose weight (1 lb/week): Eat 500 calories below your TDEE daily
- Lose weight fast (2 lbs/week): 1,000 calorie daily deficit — not recommended long-term
- Maintain weight: Eat at your TDEE
- Gain muscle (lean bulk): Eat 200–300 calories above TDEE
- Gain weight: Eat 500 calories above TDEE
Why Calorie Estimates Are a Starting Point, Not a Fixed Number
All calorie calculators — even the best ones — have a margin of error of ±10–15% due to individual variation in metabolic rate, digestive efficiency, NEAT (non-exercise activity thermogenesis), and hormonal factors. The right approach is to use this calculation as your starting point, then track your actual body weight for 2–4 weeks and adjust your intake based on real results.
If you're losing more than 1–1.5 lbs/week and not trying to, you're likely eating too little. If you're not losing weight at all on a calculated deficit, either your intake is higher than tracked, your activity is lower than estimated, or your calculated TDEE was too high.