Calorie Calculator

Checked 15 October 2026. What was checked. How these pages are maintained.

How this estimate is made

Resting calories use the Mifflin–St Jeor equation. For men: 10×kg + 6.25×cm − 5×age + 5. For women: 10×kg + 6.25×cm − 5×age − 161. Daily need ≈ that number × an activity factor. A 500 calorie daily gap is a common textbook path toward about 0.5 kg (1 lb) a week, but real change varies.

This is not medical or diet advice. Illness, medication, pregnancy, and training blocks change needs. A clinician or registered dietitian can set a target for you.

Worked example

A 40-year-old, 170 cm, 75 kg, moderately active, gets a Mifflin–St Jeor estimate around 2,400 kcal/day to maintain. Cutting 500 kcal from that is a textbook ~0.5 kg/week deficit on paper, not a promise.

Activity multipliers are rough. Desk work with a 30-minute walk is not the same as a trades job. Illness, thyroid conditions, and some medicines change needs. Not medical advice.

Resting calories, then a multiplier you pick

The resting piece is Mifflin–St Jeor. For a man it is 10 × kilograms + 6.25 × centimetres − 5 × age + 5. For a woman the constant at the end is −161 instead of +5. A 35-year-old, 170 cm, 75 kg man has a resting estimate of 1,642.5, which this page rounds to 1,643. The light-activity factor is 1.375, and 1,643 × 1.375 is about 2,258 calories a day to maintain. The same height, weight, and age for a woman is a resting estimate of 1,476.5 and a light-activity day of about 2,030. The sex box is only that constant. It is not a full model of anything else.

The factors are 1.2 sedentary, 1.375 light, 1.55 moderate, 1.725 hard, and 1.9 for a physical job plus training. They are blunt. A desk job with a daily walk is not a trades job, and two people who both pick “moderate” can burn very different amounts. Picking the higher factor because you want a larger number to eat is how the estimate stops describing you.

The 500-calorie line

The page also shows the maintain number minus 500 and plus 500, labelled as a rough half-kilogram a week. That 500 is a textbook energy gap, about 3,500 calories in a pound of body fat spread over a week. Bodies do not cash that cheque on schedule. Illness, thyroid conditions, some medicines, pregnancy, and a hard training block move the real need. Do not eat the maintain number and expect to lose weight. Do not subtract far more than 500 because a webpage offered a lower line. This is not a diet. A registered dietitian or a clinician sets a target when the stakes are medical. Pounds and inches need a conversion first: the BMI calculator will take either unit system if you only need the index, and this page wants kilograms and centimetres.

Common questions