Free Calorie Calculator

How the calorie calculator works

Your daily calorie need is your Total Daily Energy Expenditure (TDEE) — the total energy your body burns in a day. We estimate it in two steps:

1. Basal Metabolic Rate (BMR) — the calories you burn at complete rest, calculated with the Mifflin–St Jeor equation. This is the equation the Academy of Nutrition and Dietetics rates as the most accurate for most people.
2. Activity multiplier (TDEE) — your BMR multiplied by how active you are, from sedentary (×1.2) to extra active (×1.9).

To lose or gain weight, we adjust your TDEE up or down. Because about7,700 calories ≈ 1 kg of body fat (3,500 calories ≈ 1 lb), a 500-calorie daily deficit produces roughly half a kilo of loss per week.

How to use it

1. Choose your sex and units, then enter your age, height, and weight.
2. Pick the activity level that best matches a typical week.
3. Select your goal — lose, maintain, or gain — and a pace if you're changing weight.
4. Read your daily calorie target, then fine-tune the macro split (balanced, low-carb, high-protein, or keto).

How many calories should I eat a day?

There is no single answer, so here is the calculation made concrete. Both reference adults below sit near the middle of the US adult distribution — a 35-year-old woman, 5'5" (164 cm), 68 kg and a 35-year-old man, 5'10" (178 cm), 82 kg — and both are atmoderate activity (exercise 3–5 days a week). Their maintenance calories are 2122 and 2732 kcal respectively. Every target in the table is what the calculator returns for that body at that goal:

Figures in brackets are the daily change from maintenance. Your own result above is personalised and more precise than either reference body.

The activity multiplier is the biggest lever

BMR is the part of the calculation that is nearly settled science: our reference woman burns 1369 kcal a day at complete rest and the man 1763 kcal. The activity multiplier is the part you choose — and it moves the answer far more than any equation does. Here are the same two bodies across every level the calculator offers:

From sedentary to extra active is a spread of 1234 kcal a day for the same man — larger than any deficit you would deliberately choose. That is why the honest advice is to pick one level down from the one you feel you deserve. Most people overestimate: a desk job with three gym sessions is "lightly active", not "very active", and structured exercise is a smaller share of daily burn than it feels like.

Why Mifflin–St Jeor, and not one of the others

Three BMR equations are in common use. Run all three on the same two bodies and the disagreement is smaller than most people expect:

The full spread across all three is about 85 kcal for the man — roughly a banana and a coffee. Mifflin–St Jeor is the default here because it was derived on a modern population and validated as the most accurate of the three for non-obese and obese adults alike; the 1918 Harris–Benedict equation tends to read high on today's bodies. None of them measures you. An equation predicts the average person of your age, sex, height and weight, and individual resting metabolism varies around that average by roughly ±10% even before body composition is considered. Two people identical on paper can differ by 200 kcal because one carries more lean mass.

If you want to see the BMR step on its own — including how it falls with age — the BMR calculator exposes it directly, and the TDEE calculator shows the activity step.

The safe minimum, and when it overrides your pace

Weight-loss targets are clamped at 1,200 kcal for women and 1,500 kcal for men. These are the conventional thresholds below which dieting without medical supervision is discouraged, and the reason is practical rather than moral: below them it becomes genuinely difficult to get enough protein, calcium, iron and B vitamins out of food, and the risk of losing lean mass rather than fat rises sharply.

The floor is not a formality — it bites on real bodies. At an aggressive pace (1 kg a week, a 1100 kcal daily deficit), the reference woman's target lands below the floor, so the calculator returns 1200 kcal and reports the slower rate that actually follows from it — 0.8 kg a week rather than 1 kg. The reference man, with a larger maintenance, absorbs the same pace at 1632 kcal without hitting his floor.

Read that as information, not an obstacle. When the pace you asked for needs a deficit your body cannot supply, the pace is wrong for your size. Two better levers exist: raise the top of the equation by adding daily movement, or accept a slower rate that you will still be following in three months. A useful ceiling is about 1% of body weight per week — beyond that, the share of the loss coming from lean tissue climbs.

From a calorie number to actual grams of food

A calorie target on its own tells you nothing about what to put on the plate. Splitting it into macros does. Here is the reference woman's maintenance target of 2122 kcal under each preset the calculator offers:

Notice what does not change: every row is 2122 kcal. The split decides how the day feels — how full you are, how training goes, how easy the target is to hit — not whether you lose weight. Protein is the one worth setting deliberately, because it protects lean mass in a deficit and is the most satiating of the three. The macro calculator does this for your own target, and the high-protein food list shows which foods make the protein row easy to fill.

Why the scale disagrees with the arithmetic

The 7,700 kcal ≈ 1 kg rule is a first-order approximation, and treating it as a promise is how people conclude the calculator is broken. Four things bend it in practice:

• The target moves as you shrink. A lighter body has a lower BMR and spends less energy moving itself, so a fixed intake becomes a smaller deficit every month. This is the main reason linear projections overshoot — recalculate every 5 kg (10 lb).
• Adaptive thermogenesis. In a sustained deficit, non-exercise movement falls without you noticing — fewer fidgets, slower walking, more sitting — and total expenditure drops by more than body size alone predicts.
• Water masks fat. Glycogen carries roughly 3 g of water per gram, so a higher-carb weekend can hide two weeks of real loss. See signal versus noise on the progress page for how long you need to wait before a trend is real.
• Intake is under-reported. Validation studies using doubly-labelled water find self-reported intake understated by 20–30% on average. Weighing cooking oil and logging drinks usually recovers more calories than cutting a meal does.

Which is why the workflow that actually works is: take the number here, hold it for three weeks while logging honestly in the free calorie tracker, then adjust from your own measured trend rather than from any equation. After three weeks your own data is a better estimate of your maintenance than this page can be.

Calories for weight loss vs. weight gain

To lose weight, eat below your maintenance calories. A modest deficit — around the 550 kcal the moderate pace uses above — is sustainable and protects muscle. Very aggressive deficits are harder to maintain and can backfire, so this calculator caps loss targets at a safe minimum. Two things make a deficit survivable rather than merely correct: enough protein (1.6–2.2 g per kg of body weight) and enough food volume, which is what the low-calorie and high-fibre food lists are for.

To gain weight or build muscle, eat above maintenance — a surplus of 250–500 calories a day supports a lean gain when paired with resistance training and enough protein. The asymmetry is worth knowing: a deficit can be aggressive and still work, because fat loss is limited mostly by willingness, while muscle gain is limited by biology. Beyond roughly 0.25–0.5 kg (0.5–1 lb) a week for a trained lifter, the extra calories go to fat rather than muscle, so a bigger surplus buys a longer cut later rather than faster progress now.

To maintain, eat at your TDEE — but treat maintenance as a range, not a line. Body weight naturally moves 1–2 kg with water, sodium and gut contents, so maintaining means keeping a weekly average inside a band you have chosen, not hitting the same number every morning.

Accuracy and limitations

Prediction equations estimate the average person's needs at your size and activity; your true expenditure can differ by a few hundred calories. Treat the result as a smart starting point. Track your intake and weight for a couple of weeks, then nudge your calories up or down based on the trend. This tool provides general information and is not medical advice.

The specific things it cannot know about you:

• Body composition. Height and weight are a proxy for lean mass, not a measurement of it. A muscular 82 kg and a sedentary 82 kg get the same estimate and do not have the same BMR — which also means the equations read low for very muscular people and high at high body-fat percentages.
• Medication and medical conditions. Thyroid disorders, PCOS, some antidepressants and antipsychotics, and corticosteroids all shift energy expenditure or appetite. So does a recent history of dieting.
• Genuine individual variation. Two people matched on every input can differ by 200–300 kcal a day, and that is normal biology rather than an error in the equation.
• Whether you will follow it. The best target is the one you can hold for months. A theoretically optimal number you abandon in ten days is worse than a conservative one you keep.

Where to go next: see the BMR step alone in the BMR calculator, the activity step in the TDEE calculator, the pace-to-rate maths in the calorie deficit calculator, and your weight-status context in the BMI calculator. Then log the target against real food in the free calorie tracker, with per-100 g values from the USDA food database or by scanning packaged products with the barcode scanner.