Calorie Calculator — Daily Needs, BMR and TDEE

Enter your age, gender, weight, height, and activity level to calculate your daily calorie target for weight loss, maintenance, or muscle gain. Uses the Mifflin-St Jeor formula — the most accurate BMR equation in use today. Results include your suggested macro split.

Treat the Result as a Hypothesis, Not a Measurement

A calorie calculator does not measure anything. It applies an equation derived from population averages to four inputs — age, sex, height and weight — and then multiplies by an activity factor you chose about yourself. The output is a well-reasoned starting estimate for a person with your characteristics, which is not the same as a correct number for you.

That distinction matters because of how people use the figure. Treated as a measurement, a number that turns out to be 200 kcal off produces weeks of confusion and the conclusion that something is wrong with your metabolism. Treated as a starting hypothesis to be tested against two or three weeks of actual weight data, the same number does exactly what it should: it gets you close enough to start, and the results tell you the rest.

The rest of this page is about where the error comes from, so you know which part of the estimate to distrust.

The Two Halves, and Which One Is Unreliable

Every daily calorie estimate is built in two stages.

BMR — energy used at complete rest
× Activity factor — everything else you do
= Daily energy expenditure

The first stage is comparatively trustworthy. Resting metabolism tracks closely with body size and composition, and the standard equations land within roughly ten percent for most people. The exceptions are predictable: the equations were built on typical body compositions, so a very muscular person is usually underestimated and someone carrying a high proportion of fat is usually overestimated, because muscle is metabolically active tissue and fat is much less so.

The second stage is where the estimate becomes soft. The activity multiplier is a single coefficient asked to summarise a training schedule, a job, and how much you move without thinking about it — and you are the one choosing it.

Moving one step up this scale changes the final figure by a few hundred calories a day. That single dropdown carries more error than every other input combined, which is why two people with identical bodies can walk away with targets hundreds of calories apart.

The practical advice is to choose the level below the one you instinctively reach for, and describe a typical week rather than your best one. If the resulting target proves too low, the weight data will tell you within a fortnight and adjusting upward is easy.

The Part No Equation Sees

Deliberate exercise is the component people focus on and it is rarely the largest variable. The energy spent on unplanned movement — fidgeting, standing, walking between rooms, gesturing, taking stairs without deciding to — varies enormously between individuals of similar size, and no calculator asks about it because nobody can report it accurately.

It also moves on its own. When intake drops, spontaneous movement tends to fall with it: people in a deficit sit more, move less between tasks, and take the lift without noticing any decision. Expenditure therefore declines somewhat beyond what the smaller body alone would predict, which is part of why an initially effective deficit stops producing results after several weeks even when adherence has not slipped.

This is worth knowing mostly so that a stall is read correctly. It is an expected feature of the process rather than evidence of a broken metabolism, and the response is a modest adjustment or a period at maintenance, not a further large cut.

Setting a Deficit That Survives Contact With Real Life

The arithmetic of a deficit is simple. Roughly 7,700 kcal is associated with a kilogram of body mass, so a daily shortfall of around 500 kcal corresponds to something in the region of half a kilogram a week.

Two qualifications keep that from being taken too literally. Early weight change includes water and glycogen shifts that have nothing to do with fat, so the first week overstates progress and a subsequent plateau overstates failure. And the equation assumes expenditure holds constant, which the previous section explains it does not.

A more useful way to choose a deficit is by what it costs you.

• A small deficit is slow, barely noticeable, and easy to hold for months. It is almost always the right choice for someone with no deadline.
• A large deficit is faster on paper, harder to sustain, more likely to cost muscle alongside fat, and far more vulnerable to a single disrupted week.
• The best deficit is the largest one you can maintain without it dominating your week. A target that is adhered to at eighty percent for three months beats a stricter one abandoned in three weeks.

Protein intake deserves separate attention during a deficit, because it is the main lever for keeping the weight you lose weighted toward fat rather than muscle. Our body fat calculator is the tool for checking whether that is actually happening — the scale alone cannot distinguish the two.

Testing Your Own Number

Two weeks of data beats any equation. The method is deliberately unglamorous.

• Eat at the calculated maintenance figure, without a deficit, for fourteen days.
• Weigh yourself daily under the same conditions and use the weekly average rather than any single reading. Day-to-day fluctuation is mostly water and gut contents.
• Compare week one and week two averages. Stable means the estimate is close. Rising means it is too high; falling means it is too low.
• Adjust by around 200 kcal in the indicated direction and repeat. Two rounds of this will get you closer than any equation can.

The reason this works is that it measures the one thing the calculator cannot: your actual expenditure, including all the parts nobody can report. It replaces an estimate with an observation.

Where the Number Should Not Be Used

Calorie estimates are built on data from healthy adults and assume nothing unusual is happening physiologically. They do not apply during pregnancy or breastfeeding, where requirements change substantially and are managed against pregnancy-specific guidance. They do not apply to children and adolescents, whose needs are dominated by growth. They should not be used to plan intake alongside a diagnosed eating disorder, or where a medical condition or medication affects appetite, absorption or metabolism, and they are not a substitute for a dietitian where one is involved in your care.

Very low intakes carry their own problems regardless of what any arithmetic suggests. Below roughly 1,200 kcal for women and 1,500 for men, meeting micronutrient requirements from food becomes difficult, and a calculated target landing below those figures is a signal to extend the timeline rather than to eat less.

For a fuller walkthrough of setting and adjusting a target, see our guide on how many calories to eat to lose weight. For where your weight sits relative to height, the BMI calculator is a quick starting reference.