The Calorie Calculator estimates how many calories you need each day. It starts from basal metabolic rate (BMR), then multiplies by an activity factor to estimate maintenance needs. It also shows simple targets for gaining or losing weight.
Results are population estimates. Individual needs vary with body composition, genetics, medications, and health conditions.
BMR formulas
W = weight in kg, H = height in cm, A = age in years, F = body fat as a fraction of 1 (for example 0.20 for 20%).
Mifflin-St Jeor (default)
Generally considered the most accurate for most adults.
Men: BMR = 10W + 6.25H - 5A + 5
Women: BMR = 10W + 6.25H - 5A - 161
Revised Harris-Benedict
Men: BMR = 13.397W + 4.799H - 5.677A + 88.362
Women: BMR = 9.247W + 3.098H - 4.330A + 447.593
Katch-McArdle
Uses lean body mass. Often preferred when body fat percentage is known, especially in leaner people.
BMR = 370 + 21.6 × (1 - F) × W
Activity and maintenance
BMR assumes rest. Daily maintenance calories = BMR × activity factor (about 1.2 to 1.9), depending on how often and how hard you exercise.
Weight change guideline
About 3,500 Calories (kcal) is roughly 0.45 kg (1 lb) of body weight. A daily change of about 500 Calories relative to maintenance theoretically shifts weight by about 0.5 kg (1 lb) per week.
- Avoid cutting more than about 1,000 Calories per day without clinical supervision.
- Many references suggest not going below about 1,200 Calories/day for women or 1,500 for men unless a clinician is supervising.
Notes
- Mifflin-St Jeor is the usual first choice for most adults.
- Katch-McArdle needs a body fat percentage; a circumference or clinical estimate is better than a guess.
- Calorie counting is one tool among many. Food quality, protein, fiber, sleep, and activity still matter.
- Discuss major diet changes with your healthcare provider, especially if you have diabetes or take glucose-lowering medication.
