Calorie Calculator

How this calorie calculator works

The tool uses the Mifflin-St Jeor equation — the formula research has repeatedly found most accurate for estimating resting metabolism in the general population. From your age, sex, height, and weight it computes your BMR (basal metabolic rate: the energy your body burns at complete rest), then multiplies by an activity factor from 1.2 (sedentary) to 1.9 (athlete) to estimate your TDEE — total daily energy expenditure, or "maintenance calories".

Men: BMR = 10w + 6.25h − 5a + 5    Women: BMR = 10w + 6.25h − 5a − 161    (w in kg, h in cm, a in years)

Worked example

A 30-year-old man, 5′9″ and 160 lbs, has a BMR of roughly 1,680 kcal/day. With moderate exercise (factor 1.55) his maintenance is about 2,600 kcal/day. The calculator also shows −500 and +500 adjustments — the classic targets for losing or gaining roughly one pound (0.45 kg) per week.

Using the numbers well

• Be honest about activity. The most common error is overrating activity level. If you sit most of the day and train 3 times a week, "Light" or "Moderate" fits better than "Active".
• Treat it as a starting point. Individual metabolisms vary ±10% or more. Track your weight for 2–3 weeks at the suggested intake and adjust by 100–200 kcal based on what actually happens.
• Don't cut too deep. Aggressive deficits below BMR are hard to sustain and tend to sacrifice muscle. A 300–500 kcal deficit is the evidence-backed sweet spot for most people.
• Recalculate as you change. A lighter body burns fewer calories, so update the numbers every 10 lbs or so of progress.

Frequently asked questions