Calorie Calculator
Estimate how many calories you need a day to maintain, lose or gain weight, using the Mifflin-St Jeor equation and your activity level.
Estimate resting energy needs and daily maintenance calories from height, weight, age and sex. The calculator applies the simplified Mifflin-St Jeor equation, then an activity multiplier and your selected calorie adjustment. These are planning estimates for adults, not a prescription or a prediction of weekly weight change.
How to use this tool
- Enter your sex, age, height and weight in the selected units.
- Choose the activity description closest to a typical week.
- Select maintenance or a daily calorie deficit or surplus.
- Compare the estimate with the other adjustments in the table.
Formula
Resting kcal/day = 10W + 6.25H − 5A + 5 (male) or −161 (female); maintenance = resting estimate × activity factor; target = maintenance + adjustment
W is kilograms, H centimetres and A years. Activity multipliers 1.2, 1.375, 1.55, 1.725 and 1.9 are broad calculator assumptions; exercise frequency alone cannot measure energy expenditure. The original Mifflin sample was aged 19–78, so estimates beyond that range involve extrapolation.
Example
For a 30-year-old man weighing 80 kg at 180 cm, resting energy = 800 + 1,125 − 150 + 5 = 1,780 kcal/day. At multiplier 1.55, maintenance is 2,759 kcal/day. A selected 500-kcal deficit gives 2,259 kcal/day, without implying a guaranteed rate of weight loss.
Frequently asked questions
Why is weekly weight loss not predicted?
A fixed calorie deficit does not produce a fixed long-term weight change. Metabolism and energy needs change with body weight, and actual intake and activity vary.
Are lower calorie targets automatically safe?
No. This tool suppresses targets below 1,000 kcal/day and flags low intakes; those limits are not personal safety thresholds. A clinician or dietitian can assess individual needs.
Who should not use this estimate?
It is not designed for children, pregnancy or breastfeeding. Medical conditions, medications and recovery from illness can also change energy needs.
Sources
This tool gives an estimate for general information only. It is not financial, tax, legal or medical advice — check with a qualified professional before you rely on the result.
Last updated: 2026-10-30