Calorie Calculator
Calorie calculator: your BMR and TDEE from the Mifflin-St Jeor formula, with calorie targets, macros and goal planner. Free, no sign-up, and it runs in your browser.
Dedicated page: /en/calorie-calculator
The Mifflin-St Jeor formula uses a different constant for men and women.
Mifflin-St Jeor is the most accurate for most people. Katch-McArdle is better if you are lean and know your body fat.
Enter a target weight to see how long it takes at your current pace.
0.7 to 1.0 g per lb is the usual range for active adults.
Estimate only, not medical advice. BMR and TDEE are averages; your real burn depends on muscle mass, hormones, and how active you really are. Do not eat below 1,200 calories a day (women) or 1,500 (men) without a doctor, and talk to a clinician before a big diet change.
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Quick answer
A calorie calculator works out your BMR and TDEE from the Mifflin-St Jeor formula. Enter your sex, age, height, weight and activity level, and it gives your maintenance calories, targets for losing, maintaining or gaining weight, macros in grams, and a goal-weight planner.
About this Calorie Calculator
Calorie calculator: your BMR and TDEE from the Mifflin-St Jeor formula, with calorie targets, macros and goal planner. It is one of the Health and Family on ToolUstad, and like every tool here it runs entirely in your browser: nothing you type, paste or open is uploaded to a server, and there is no sign-up or usage limit.
What is a calorie calculator?
A calorie calculator answers the question at the centre of every diet: how many calories do I burn in a day? The answer has two parts. Your BMR, basal metabolic rate, is what your body burns at rest, just to keep you alive: breathing, circulation, cell repair. Your TDEE, total daily energy expenditure, is your BMR times an activity factor, from 1.2 for sedentary to 1.9 for extremely active. TDEE is the calories you need to maintain your current weight. A 35-year-old woman, 165 lb and 5 ft 6 in, moderately active, has a BMR of 1,460 calories a day and a TDEE of 2,263. To lose 1 lb a week she eats 1,763 calories a day, a deficit of 500.
BMR formulas: Mifflin-St Jeor, Harris-Benedict and Katch-McArdle
Three formulas are on the page, because no single formula is right for everyone. Mifflin-St Jeor is the default and the most accurate for most people: 10 times weight in kg, plus 6.25 times height in cm, minus 5 times age, plus 5 for men or minus 161 for women. Revised Harris-Benedict, from 1984, is older and usually reads a little higher. On the example woman it gives a BMR of 1,507, against 1,460 for Mifflin-St Jeor. Katch-McArdle is different: it works from lean body mass, not total weight. On the same woman at 20% body fat, it gives a BMR of 1,663.
Activity levels, targets and macros
The activity factor is where most calculators go wrong, because people overestimate how active they are. Sedentary is 1.2, lightly active 1.375, moderately active 1.55, very active 1.725, extremely active 1.9. The calculator shows your TDEE at all five levels. One pound of body fat is about 3,500 calories. A daily deficit of 500 calories is 3,500 a week, about 1 lb a week. The targets table shows six goals: maintain, mild loss, loss, extreme loss, and mild and regular gain. Do not go below 1,200 calories a day for women or 1,500 for men without a doctor.
Calories are not the whole story. Protein protects muscle while you lose weight, and the calculator sets it from bodyweight: 0.8 g per lb by default, which is 132 g a day for the 165 lb example. Fat is set at 30% of calories, and the rest goes to carbs. On 1,763 calories a day, that is 132 g of protein, 59 g of fat and 181 g of carbs. Enter a goal weight and the calculator tells you how long it takes: from 165 lb to 150 lb at 1 lb a week takes 15 weeks.
Best practices
- Track for two weeks before you change anything: most people underestimate what they eat by 20% to 30%.
- Hit the protein target: 0.8 g per lb of bodyweight protects muscle while you lose fat.
Common mistakes to avoid
- Eating at your BMR instead of your TDEE minus a deficit: BMR is what you burn lying still, not what you need.
- Crash dieting at 1,000 calories: it loses muscle as well as fat.
Who is the calorie calculator for?
Anyone starting a diet, trying to gain weight or muscle, or checking a target after a plateau.
This calculator is an estimator, not medical advice. BMR formulas are accurate to about 10%, and your real TDEE depends on your actual activity, muscle mass and health. If you have a medical condition, are pregnant, or are under 18, talk to a doctor or a registered dietitian before changing your diet.
Learn: how to use the Calorie Calculator
- Pick imperial or metric, then enter your sex, age, height and weight.
- Choose the BMR formula: Mifflin-St Jeor is the default, Harris-Benedict and Katch-McArdle are options.
- Pick your activity level and your goal: lose, maintain or gain.
- Read your BMR, TDEE, target calories, macros and the time to your goal weight.
Features
- Mifflin-St Jeor BMR, plus revised Harris-Benedict and Katch-McArdle formulas
- TDEE at all five activity levels, from sedentary to extremely active
- Calorie targets for maintain, mild loss, loss, extreme loss and gain
- Macros in grams: protein from bodyweight, fat at 30%, rest to carbs
- Metric and imperial units, with conversion when you switch
- Weekly weight-change projection and a goal-weight planner with a date
- Food energy converter: kilocalories to kilojoules
Worked example
A 35-year-old woman, 165 lb and 5 ft 6 in, moderately active: BMR is 1,460 calories a day and TDEE is 2,263 calories. To lose 1 lb a week she eats 1,763 calories a day. At 0.8 g of protein per lb of bodyweight, that is 132 g of protein a day. The same woman on the Harris-Benedict formula has a BMR of 1,507, and on Katch-McArdle at 20% body fat it is 1,663.
Frequently asked questions
What is BMR?
Basal metabolic rate: the calories your body burns at complete rest, just to keep you alive, breathing, circulation and cell repair. It is 60% to 70% of what most people burn in a day.
What is TDEE?
Total daily energy expenditure: your BMR times an activity factor, from 1.2 for sedentary to 1.9 for extremely active. It is the calories you need to maintain your current weight.
Which BMR formula is most accurate?
Mifflin-St Jeor is the most accurate for most people. Harris-Benedict, from 1984, usually reads a little higher. Katch-McArdle is best if you are lean and know your body fat, because it works from lean mass.
How big a deficit should I use to lose weight?
300 to 500 calories a day below maintenance, for 0.5 to 1 lb a week. A bigger deficit loses weight faster but also loses more muscle and is harder to keep. Do not go below 1,200 calories a day (women) or 1,500 (men) without a doctor.
Why did my weight not move this week?
Water, glycogen and muscle move the scale by pounds day to day. Judge by the 4-week average, not one weigh-in, and weigh at the same time of day.
How many calories should I eat to lose weight?
Eat 300 to 500 calories below your TDEE. On a TDEE of 2,263, that is 1,763 to 1,963 calories a day, for 1 lb a week or a little less. A bigger deficit loses weight faster but also loses more muscle.
How much protein do I need?
About 0.8 g per lb of bodyweight a day for most people, up to 1 g per lb if you lift weights. On 165 lb, that is 132 g to 165 g a day. Spread it across meals, about 30 g per meal.
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