How the calorie calculator works
First, the calculator estimates your basal metabolic rate (BMR), the calories your body burns at rest,
using the Mifflin-St Jeor equation. It then multiplies your BMR by an activity factor to estimate your
total daily energy expenditure (TDEE): the calories you burn on a typical day.
The Mifflin-St Jeor equation
Men: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5
Women: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161
TDEE = BMR × activity factor (from 1.2 for sedentary to 1.9 for extra active).
Example
A 30-year-old man, 175 cm and 75 kg, has a BMR of 10 × 75 + 6.25 × 175 − 5 × 30 + 5 = 1,699 kcal.
If he's moderately active, his TDEE is 1,699 × 1.55 ≈ 2,633 kcal a day.
Using your numbers to lose or gain weight
- One kilogram of body fat stores roughly 7,700 kcal (about 3,500 kcal per pound).
- A daily deficit of 500 kcal loses about 0.5 kg (1 lb) per week.
- For muscle gain, a small surplus of 250–500 kcal combined with strength training works best.
- Recheck your numbers every few kilograms, because your needs drop as you lose weight.
Frequently asked questions
How many calories should I eat to lose weight?
A deficit of about 500 calories a day below your maintenance level (TDEE) leads to roughly 0.5 kg (1 lb) of weight loss per week. Most experts advise not going below about 1,200 calories a day for women or 1,500 for men without medical supervision.
What is the difference between BMR and TDEE?
BMR (basal metabolic rate) is the energy your body uses at complete rest to keep you alive. TDEE (total daily energy expenditure) adds everything else: walking, working, exercise and digesting food. TDEE is the number you eat to maintain your weight.
How accurate is this calorie calculator?
The Mifflin-St Jeor equation is one of the most accurate formulas for estimating BMR, typically within about 10% for most people. Treat the result as a starting point and adjust based on how your weight changes over a few weeks.
Which activity level should I choose?
Be honest and conservative. Most people with office jobs who exercise a few times a week are lightly or moderately active. Overestimating your activity is the most common reason calorie targets don't work as expected.