Estimate how many calories you burn each day based on your age, size and activity level, using the Mifflin-St Jeor equation. See your BMR, your daily energy needs, and targets to lose, maintain or gain weight.
Calorie Calculator
How the Calorie Calculator Works
This calculator estimates how many calories your body burns in a day, and turns that into practical daily targets for losing, maintaining or gaining weight. People use it when starting a diet, planning a training block, or simply checking whether their usual eating roughly matches what their body needs. Because it is built from your age, sex, height, weight and activity level, the estimate is personalised far beyond the generic “2,000 calories a day” printed on food labels.
It starts with the Mifflin-St Jeor equation, the formula most dietitians currently consider the most reliable for estimating basal metabolic rate (BMR) — the energy you burn at complete rest. For men, BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5. For women, the same formula ends with −161 instead of +5. Your BMR is then multiplied by an activity factor to estimate your total daily energy expenditure (TDEE): 1.2 for sedentary, 1.375 for lightly active, 1.55 for moderately active, 1.725 for very active and 1.9 for extra active.
The result panel shows your BMR, your maintenance calories (the TDEE itself), and two adjusted targets: maintenance minus 500 calories for steady weight loss of roughly half a kilogram a week, and maintenance plus 500 for gradual gain. For safety, the calculator never suggests a loss target below 1,200 calories a day. Be honest about activity — it is the input people most often overestimate, and it changes the answer more than any other.
How to Use This Calculator
- Enter your age and select your sex — the formula uses a different constant for men and women.
- Add your height and current weight in the units offered.
- Pick the activity level that matches your typical week, not your best week: desk work with little exercise is sedentary, training most days is very active.
- Press Calculate and note your maintenance number first — that is your baseline.
- Choose the lose or gain target if you have a goal, and re-run the calculator after every 5 kg or so of change, because a lighter body burns fewer calories.
Example
A 30-year-old man, 175 cm and 75 kg, who exercises 3–5 days a week (factor 1.55): his BMR is (10 × 75) + (6.25 × 175) − (5 × 30) + 5 = 1,698.75 calories, and his maintenance needs are 1,698.75 × 1.55 ≈ 2,633 calories a day. The calculator’s loss target for him is about 2,133 calories and its gain target about 3,133 calories.
For comparison, a woman of the same age, height and weight with a sedentary lifestyle (factor 1.2) has a BMR of 1,532.75 calories and maintenance needs of about 1,839 calories a day — a good illustration of how much the sex constant and activity level together move the answer.
Understanding Your Result
Maintenance calories are the centre of everything: eat near them and your weight should stay roughly steady over time. The ±500-calorie targets are deliberately moderate — a daily 500-calorie deficit adds up to about 3,500 calories a week, roughly half a kilogram of body fat, which is a pace most people can sustain without feeling deprived. Faster loss usually costs muscle as well as fat, and very low intakes risk nutrient gaps, which is why the loss target is floored at 1,200 calories.
Remember that every figure here is an estimate. The Mifflin-St Jeor equation is typically within about 10% for most people, but real metabolism varies with muscle mass, hormones, medication, sleep and how much you fidget through the day. Use the numbers as a starting plan, watch your actual weight trend for three to four weeks, and adjust by 100–200 calories if reality disagrees with the estimate. If you have a medical condition, are pregnant or breastfeeding, or have a history of eating disorders, please talk to a doctor or registered dietitian before following any calorie target — this calculator is general information, not medical advice.
One more practical point: whatever target you follow, protein deserves attention. Eating enough protein — and keeping up some resistance exercise — helps make sure the weight you lose comes mostly from fat rather than muscle, and the weight you gain is more likely to be muscle rather than fat. The calculator sets the energy total; what you build that total from is up to you.
Calorie Calculator FAQs
How many calories should I eat to lose weight?
A common, sustainable approach is about 500 calories a day below your maintenance level, which this calculator shows as its loss target. Slower deficits also work and are often easier to keep up.
Why does the calculator ask for my sex?
The Mifflin-St Jeor equation uses a different constant for men (+5) and women (−161), reflecting average differences in body composition. Leaving it out would make the estimate noticeably less accurate.
What if my weight is not changing at my “maintenance” calories?
Then your true maintenance is a little different from the estimate — most likely your activity factor was optimistic. Lower the intake slightly or raise daily movement; your measured trend always beats the formula.
Are 1,200-calorie diets safe?
The calculator never sets a loss target below 1,200 calories a day, a commonly used safety floor for adults. Diets below that should only be followed under medical supervision.
Do these targets work for athletes in training?
Only roughly. Heavy training blocks, endurance events and muscle-building phases can need considerably more energy and specific protein targets. Athletes are better served by a sports dietitian for precise plans.
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