What this calculator does
It estimates two numbers: your basal metabolic rate (BMR), which is what you burn at rest, and your total daily energy expenditure (TDEE), which adds movement and exercise.
It uses the Mifflin-St Jeor equation, one of the most widely used predictive formulas for adults, and an activity multiplier you choose.
The formula
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 factorActivity factors: sedentary 1.2, light 1.375, moderate 1.55, active 1.725, very active 1.9.
A worked example
A 30-year-old man, 80 kg, 180 cm, moderate activity:
- BMR: 800 + 1,125 − 150 + 5 = 1,780 kcal
- TDEE: 1,780 × 1.55 = 2,759 kcal
A 30-year-old woman, 60 kg, 165 cm, light activity:
- BMR: 600 + 1,031.25 − 150 − 161 = 1,320 kcal
- TDEE: 1,320 × 1.375 = 1,815 kcal
Why the number moves
BMR falls with age and with lost muscle mass. It rises with body size. Exercise adds on top, but the activity factor is a blunt instrument: an hour of hard training is not the same as an hour of walking. The equation also does not know about thyroid conditions, medication, pregnancy or illness.
What this calculator does not do
It does not prescribe a diet, diagnose a metabolic condition, or replace a dietitian. It does not account for pregnancy, breastfeeding, children, or athletes with very high training loads. Use it as a starting estimate, then adjust with real-world results.
Why the first estimate is rarely the final one
Use the number for two to three weeks, weigh yourself under the same conditions, and adjust by 100–200 kcal if the trend is not what you expected. The equation gives a starting point; your data gives the correction.
Frequently asked questions
What is the difference between BMR and TDEE?
BMR is the energy you burn at complete rest. TDEE is BMR multiplied by an activity factor, so it includes movement, exercise and digestion. TDEE is the number to compare with what you eat.
Which activity factor should I choose?
Sedentary is desk work with little exercise, light is one to three sessions a week, moderate is three to five, active is six to seven, and very active is physical work plus training. When in doubt, pick the lower one — most people overestimate activity.
Is TDEE exact?
No. The equation predicts a population average; individual metabolism can differ by 10% or more. Treat the result as a starting point, then adjust based on what your weight actually does over two to three weeks.
How many calories should I cut?
A common starting point is 300–500 kcal below TDEE for gradual loss, but the right number depends on your goal and health. This page does not give medical or dietetic advice.