Calorie Calculator
Runs locallyInput stays in your browserFree, no sign-up
How much should you eat in a day? The answer sits in two numbers: your basal metabolic rate (BMR) and your total daily energy expenditure (TDEE). This calculator estimates BMR with the Mifflin-St Jeor equation — for men, 10 x weight in kg + 6.25 x height in cm - 5 x age + 5; for women, the same formula ends in -161 instead of +5. It then multiplies BMR by your activity factor — 1.2 for sedentary, 1.375 for lightly active, 1.55 for moderately active, 1.725 for very active, 1.9 for extra active — to give TDEE. Finally it adjusts for your goal: -500 for weight loss, -250 for slow loss, 0 for maintenance, +250 for slow gain, +500 for muscle gain.
Three everyday uses cover most people. First, anyone losing weight: find your maintenance level, then see the cutting target, so a takeaway meal can be judged as a share of the whole day rather than by guesswork. Second, anyone training for muscle: TDEE differs between training and rest days, and the gaining target is a starting point to test for two weeks against the scale before adding more food. Third, anyone starting to track food at all: until you know your maintenance level, you cannot tell whether you are over or under eating, and every diet decision is guesswork.
The limits matter as much as the numbers. The equation is built for healthy adults: it is unreliable for pregnant or breastfeeding women, teenagers, people with very high or very low body fat, and anyone with a metabolic condition such as thyroid disease — none of those cases should treat the result as medical advice. Inputs are bounded too: age 10 to 100, weight 20 to 300 kg, height 100 to 250 cm, and out-of-range values produce a warning instead of a result. Imperial units work directly: pick lb for weight and in for height, and the tool converts first at 1 lb = 0.4536 kg and 1 in = 2.54 cm.
Alongside the target calories you get a macronutrient split — protein at 1.8 g per kilogram of body weight, fat at 30% of target calories, carbohydrates filling the rest — plus an estimated weekly weight change derived from the daily calorie gap. Everything runs in your browser: your weight, age and other inputs are never sent to a server, and opening the page on another device shows none of your entries.
How to use
- Pick your sex, then enter age, weight and height — weight in kg or lb, height in cm or in.
- Choose an activity level. When in doubt, pick one lower: a desk job with fewer than three sessions a week is sedentary or lightly active.
- Choose a goal: lose weight, lose slowly, maintain, gain slowly, or gain muscle. The target is TDEE plus or minus the goal adjustment.
- Read your BMR, TDEE, target calories and macro split, and copy the result to share it or save it in your notes.
FAQ
What is the difference between BMR and TDEE?
BMR is what your body burns at complete rest just to keep you alive, determined only by sex, weight, height and age. TDEE is BMR multiplied by an activity factor, so it also covers work, walking and exercise. Weight-loss or muscle-gain targets are set from TDEE, not from BMR alone — eating at your BMR level usually means eating far too little.
Why do men and women with the same stats differ by 166 kcal?
The Mifflin-St Jeor equation differs only in its constant: +5 for men, -161 for women, a gap of exactly 166 kcal. That is an empirical correction for average body-composition differences, not a personal measurement. If your body fat is well above or below average, the formula's error grows, so treat the result as a starting estimate.
What happens if I pick too high an activity level?
Each step up adds roughly 10% or more to TDEE, so your target inflates with it — and someone cutting weight can end up eating at maintenance without realising it. When in doubt, pick one level lower: a desk job with fewer than three sessions a week is sedentary or lightly active. Hold that level for two weeks, then adjust if your weight is not moving as expected.
How fast will I lose weight on a 500 kcal daily deficit?
Using the rule of thumb that 7,700 kcal equals about 1 kg of body weight, a 500 kcal daily deficit works out to roughly 0.45 kg per week, or about 1.8 kg per month. Real progress is not a straight line: water weight, training changes and metabolic adaptation all bend the curve. If your target falls below 1,200 kcal for women or 1,500 kcal for men, the page warns you — a very low-calorie diet long term should be discussed with a doctor first.
Why are protein, fat and carbs split this way?
Protein is set at 1.8 g per kilogram of body weight to help preserve muscle while losing fat. Fat takes 30% of target calories, enough for hormone production and fat-soluble vitamin absorption. Carbohydrates fill whatever calories remain, because they are the easiest variable to scale with total intake. This split suits healthy adults; pregnant or breastfeeding women, teenagers and competitive athletes should follow a clinician's or dietitian's plan instead.