Your body burns calories even when you’re doing nothing at all. Breathing, keeping warm, running your heart and brain: all of it takes energy. Add the energy you spend on moving around, and you get the number of calories you use in a whole day. This calculator estimates both. Enter your sex, age, height, weight and how active you are, and it shows your BMR and your TDEE.
BMR (basal metabolic rate) is the energy your body needs at complete rest just to keep you alive. Think of it as the cost of staying switched on.
TDEE (total daily energy expenditure) is your BMR plus everything else: walking, working, exercising and digesting food. It’s the realistic estimate of what you burn in a normal day.
If you eat roughly your TDEE, your weight tends to stay stable. Eat less over time and you’ll tend to lose weight. Eat more and you’ll tend to gain.
Choose your units (metric or imperial).
Enter your sex, age, height and weight.
Pick the activity level that best matches a typical week for you.
Read your BMR and TDEE.
Be honest with the activity level. Most people overestimate it, and that inflates the result. If you’re between two levels, choose the lower one.
The calculator uses the Mifflin-St Jeor equation, which is widely used and generally considered one of the more reliable options for the general population:
Men: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5
Women: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161
Then TDEE = BMR × activity factor:
Activity level
Description
Factor
Sedentary
Desk job, little or no exercise
1.2
Lightly active
Light exercise 1 to 3 days a week
1.375
Moderately active
Moderate exercise 3 to 5 days a week
1.55
Very active
Hard exercise 6 to 7 days a week
1.725
Extra active
Very hard exercise plus a physical job
1.9
Example 1. A man, 30 years old, 80 kg, 180 cm, exercising 3 to 5 days a week.
BMR: 800 + 1,125 − 150 + 5 = 1,780 calories
TDEE: 1,780 × 1.55 = about 2,759 calories
Example 2. A woman, 35 years old, 65 kg, 165 cm, with light exercise once or twice a week.
BMR: 650 + 1,031.25 − 175 − 161 = about 1,345 calories
TDEE: 1,345 × 1.375 = about 1,850 calories
Your TDEE is a reference point, not a target you must hit. A common rule of thumb is that about 7,700 calories equal one kilogram of body weight (roughly 3,500 per pound). That gives a rough sense of scale:
Eating around 500 calories below your TDEE each day leads to roughly 0.5 kg (a pound) of loss per week, in theory.
Eating around 300 to 500 calories above it each day is a modest surplus often used for gradual weight gain.
Treat these as estimates. Real bodies adapt, so the rate of change usually slows over time, and water, hormones and muscle changes make the scale jump around. Small, steady adjustments are easier to keep up than big cuts, and extreme restriction can cost you muscle, energy and health.
The formulas work on averages, and you’re not an average. Your actual calorie burn can vary with:
Muscle mass. Muscle burns more energy than fat, even at rest. Two people with the same height, weight and age can have different BMRs.
Genetics and hormones. Thyroid function and other conditions can change your metabolism.
Sleep, stress and illness. All of these can shift how much you burn and how hungry you feel.
Age. Energy needs generally decline as you get older, partly because muscle mass drops.
Pregnancy and breastfeeding. Needs rise during these periods, and the standard formulas don’t account for it.
The best way to check is to track your weight and intake for a few weeks. If your weight doesn’t move as expected, adjust the estimate rather than the other way round.
Overestimating activity. One workout a week doesn’t make you “very active”. When in doubt, go lower.
Cutting calories too far. A very low intake isn’t safe for most people to sustain without medical supervision.
Eating back every exercise calorie. The numbers shown on fitness trackers and gym machines are often inflated.
Treating the result as exact. Plan with a range, for instance 100 to 200 calories either side of the figure.
Ignoring food quality. Calories are only part of the story. Protein, fibre, vitamins and minerals matter for how you feel and how your body works.
Is BMR the same as the calories I should eat?
No. BMR is only what you burn at rest. Most people burn considerably more than that over a full day, which is what TDEE measures. Eating at your BMR alone, for a long time, isn’t a recommended plan.
Which formula does this calculator use?
The Mifflin-St Jeor equation. Other formulas exist, such as Harris-Benedict and Katch-McArdle, and they can give slightly different results.
Why is my result different from another website’s?
Different sites use different formulas and activity multipliers. A gap of a hundred calories or so is normal. Pick one tool and stick with it so you can compare your results over time.
How accurate is the estimate?
It’s a reasonable starting point for most healthy adults, but it can be off by a few hundred calories in either direction. Adjust it according to what actually happens to your weight.
Should I recalculate when my weight changes?
Yes. As your weight, activity or age changes, so does your TDEE. Recalculating every few months keeps the estimate useful.
Can I use this for children, teenagers or pregnant women?
No. The equation is designed for healthy adults. Growing bodies and pregnancy have different needs, so please ask a doctor or a registered dietitian.
This calculator provides estimates for general information only and is not medical or nutritional advice. If you have a medical condition, are pregnant or breastfeeding, take medication, or are planning a significant change to your diet, please speak to a doctor or a registered dietitian first.