The formula
How it works
Find how many calories you should eat each day to lose, maintain or gain weight. The calculator estimates the calories you burn from your body and activity, then adjusts for your goal.
FAQ
How big a deficit is safe?
A deficit of about 500 calories a day loses roughly half a kilo (a pound) a week, which is a sustainable pace. Larger deficits lose faster but are harder to keep up and can cost muscle if protein is too low.
Why do two people the same weight need different calories?
Age, height, sex and especially activity all change the total. Muscle also burns more than fat, so body composition matters — which is why the same weight can come with quite different calorie needs.
What is BMR and how is it different from the daily target?
BMR is the energy your body burns at complete rest just to keep organs running. The daily target multiplies BMR by an activity factor and adds your goal adjustment, so it is always higher than BMR unless you are almost entirely sedentary.
Which activity level should I choose?
Pick the level that matches your typical week, not your best week — most people who don’t exercise structured workouts fall under sedentary or light, even if they’re on their feet at work. Overestimating activity is the most common reason the target ends up too high.
Should I recalculate as I lose or gain weight?
Yes — BMR drops as body weight drops, so a target set for your starting weight becomes too generous after losing 5–10% of it. Re-enter your current weight every few weeks to keep the calorie target accurate.
Does this account for muscle mass or body fat percentage?
No, the Mifflin-St Jeor formula used here only needs sex, age, height and weight, so it doesn’t separate muscle from fat. Very muscular or very lean people may burn somewhat more than it predicts, and it’s less accurate for those with a lot more body fat than average.
Is it safe to eat below the calculated maintenance level long-term?
Short deficits of 500–1000 calories a day are generally fine, but eating far below BMR for extended periods can slow metabolism and cause muscle loss. Anyone eating under about 1,200 (women) or 1,500 (men) calories a day should check with a doctor or dietitian.
About the calorie calculator
This calculator estimates how many calories you should eat in a day to reach a weight goal — losing, maintaining or gaining. It starts from the energy your body burns at rest, scales it up for how active you are, and then adds or subtracts calories depending on whether you want to lose or gain. The result is a daily target you can eat around, which is the foundation of nearly every diet or fitness plan.
How to use it
Enter your sex, age, height and weight, choose your activity level, and pick a goal. The calculator shows your maintenance calories — the amount that keeps your weight steady — along with the target for your chosen goal. For example, a moderately active 30-year-old man of 180 cm and 80 kg maintains on around 2,750 calories, and would eat about 2,250 to lose half a kilo a week. Adjust the activity level honestly, as overestimating it is the most common mistake.
The formula
Maintenance calories are your basal metabolic rate times an activity factor, using the Mifflin-St Jeor equation for the BMR. The goal then shifts this figure: , where the adjustment is about −500 or −1000 to lose weight, and +500 or +1000 to gain. A pound of fat holds roughly 3,500 calories, which is why a 500-a-day change moves weight by about a pound a week.
Where it is used
This is the starting point for almost any structured approach to eating. Dietitians and trainers use it to set calorie targets for clients, fitness apps calculate it behind the scenes, and anyone counting calories uses it as the line to aim above or below. Pairing the target with a macro calculator turns a single calorie number into a full plan for protein, carbohydrate and fat.