Work out how many calories you need a day to maintain your weight, and what to eat instead if you want to lose or gain. Uses the Mifflin–St Jeor equation and shows every step.
| Activity level | Maintain | Your goal |
|---|
A 30-year-old man weighing 75.0kg at 178cm who is moderately active needs about 2,662 kcal a day to stay the same weight.
Show your working
Breakdown
- At rest (BMR)
- 1,718 kcal
- Burned through activity
- 945 kcal
- Daily total to maintain
- 2,662 kcal
- Your goal target
- 2,662 kcal
Assumptions
- Mifflin–St Jeor is used, the equation most widely recommended when body composition is unknown.
- The activity multiplier (×1.55) is a convention, not part of the published equation — treat the daily total as less precise than the resting figure.
- Predictive equations typically land within about 10% of measured resting expenditure.
- A 500 kcal daily deficit is the conventional figure for about half a kilo a week; expenditure falls as weight is lost.
- Not medical advice; discuss any significant change in intake with a clinician.
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Calorie facts
- How many calories do I need a day?
- A moderately active 30-year-old man at 75 kg and 178 cm needs about 2,662 kcal a day to maintain his weight.
- How many calories to lose weight?
- Take about 500 kcal a day off maintenance — 2,162 kcal in that example — for roughly half a kilo a week.
- What is the difference between BMR and daily calories?
- BMR is what you burn at complete rest — 1,718 kcal in that example. Daily calories add everything you do on top.
- Which formula does this use?
- Mifflin–St Jeor, published in 1990 and the equation most widely recommended when body composition is unknown.
How your daily calorie need is worked out
It is two steps. First your basal metabolic rate — the energy your body uses keeping you alive at complete rest, before you move at all. Then that figure is multiplied by an activity factor to give the calories you actually burn in a day.
The resting figure comes from the Mifflin–St Jeor equation, published in 1990 and derived from measurements of 498 healthy adults. It is the equation most often recommended when body composition is unknown, and it predicts resting expenditure within about 10% of the measured value for most people.
Eating to lose or gain
Eat at your maintenance figure and your weight holds steady. Eat below it and you lose; above it and you gain. The conventional figure is that a 500 kcal daily deficit costs about half a kilo a week, and 250 kcal about a quarter of a kilo.
Treat that as a starting point, not a promise. As you lose weight your body becomes smaller and burns less, so the same deficit slows over time. Re-run the numbers every few kilos rather than holding one target for months.
Choosing an activity level honestly
Sedentary ×1.2
A desk job and little deliberate exercise. Walking to the shops does not move you up a band.
Lightly active ×1.375
Light exercise one to three days a week.
Moderately active ×1.55
Genuine moderate exercise three to five days a week.
Very active ×1.725
Hard exercise six or seven days a week.
Extra active ×1.9
Training twice a day, or a physically demanding job on top of exercise.
If you are unsure
Pick one level lower than you think. Eat at that figure for two or three weeks and adjust by 100–200 kcal depending on which way the scales move.
Worked example
Male, 30 years old, 75 kg, 178 cm, moderately active. BMR = (10 × 75) + (6.25 × 178) − (5 × 30) + 5 = 750 + 1,112.5 − 150 + 5 = 1,717.5 kcal. Multiplied by 1.55 for activity, that is 2,662 kcal a day to maintain. To lose about half a kilo a week, eat 2,162 kcal.
Important notes
These figures are estimates for healthy adults and are not medical advice. Pregnancy, breastfeeding, thyroid conditions, some medications and a history of disordered eating all change what is appropriate — talk to a clinician rather than a calculator. The equation was derived from adults aged 19 to 78 and should not be used for children.
Evidence & Methodology
How This Page Is Grounded
Method
Estimates resting energy expenditure with the Mifflin–St Jeor equation, multiplies it by the selected activity factor for daily needs, then applies a fixed deficit or surplus for the chosen weight goal.
Important limitation: Population equations differ from an individual’s measured metabolism; activity factors are a convention rather than a published finding, so the daily total is less precise than the resting figure. Deficit-to-weight-loss rates are approximations that slow as weight is lost.
Primary Sources
Quality Checks
Male and female equations, unit conversion, activity multipliers and goal offsets are checked against worked examples derived from the source equation.
See how sources are selected and corrections are handled in our Editorial & Calculation Methodology, and which automated checks this page has to pass in How We Test.