Calorie Calculator

Your daily calorie need is the amount of energy your body uses in a day. Eat around that number and your weight holds steady; eat consistently above or below it, and you gain or lose. That is the whole game. This calculator estimates your number from your age, sex, height, weight and activity level, then turns it into clear targets for maintaining, losing or gaining.

How your calorie target is worked out

The calculation happens in two steps. First it estimates your Basal Metabolic Rate (BMR) — the calories you would burn lying in bed all day — using the Mifflin-St Jeor equation, which a systematic comparison of predictive equations rates as the most accurate for the general population. Then it multiplies that BMR by an activity factor to get your Total Daily Energy Expenditure (TDEE): everything you burn on a normal day, movement and digestion included.

Enter your height and weight in whichever units you have — kilograms and centimetres, or pounds, feet and inches — the calculator converts automatically.

That two-step method is exactly what people mean when they ask “how do I calculate my calories,” and it is the same maths the BMR calculator and TDEE calculator break out in more detail if you want to see each stage on its own.

How to calculate a calorie deficit

A calorie deficit is simply eating fewer calories than you burn — the one thing every kind of weight loss has in common. To find yours, start from your maintenance number and subtract the gap you want to run:

1. Work out your maintenance calories (the TDEE above).
2. Subtract 500 kcal for a steady loss of about 0.5 kg (1 lb) a week, since roughly 7,700 kcal equals 1 kg of body fat (about 3,500 kcal per pound).
3. Prefer a gentler pace? A 250 kcal/day deficit trims about 0.25 kg a week and is far easier to live with.

So someone who maintains at 2,400 kcal would eat around 1,900 for a moderate deficit. The calculator does this for you and shows the loss and gain targets right next to your maintenance figure, so you never have to do the subtraction by hand.

One caution worth repeating: bigger is not better. Very aggressive deficits stall your progress, eat into muscle, and are miserable to sustain. Most guidelines cap sensible loss at around 500–750 kcal/day below maintenance for exactly that reason.

Choosing a target

• Maintain: eat at your TDEE.
• Lose weight: a 250–500 kcal/day deficit is sustainable for most people.
• Gain weight or muscle: a 250–500 kcal/day surplus, paired with resistance training, favours lean gains over fat.

Whatever you pick, the quality of those calories still matters — how you split them between protein, carbs and fat shapes your energy, your hunger, and how much of any change is muscle rather than fat. Our macro calculator turns a calorie target into a protein-carb-fat breakdown. And if you only want your maintenance line on its own, the maintenance calorie calculator focuses on that single number.

Zigzag (calorie cycling)

The calculator also shows a zigzag schedule — seven days that alternate higher and lower intakes but add up to the same weekly total as eating at maintenance every day. Some people find cycling calories this way easier to sustain (bigger meals on training or social days), and it can dodge the plateau feeling of a flat daily number. The weekly average is what counts, so any pattern that hits the same total works.

You can also switch the results between kcal and kilojoules (kJ) — 1 kcal = 4.184 kJ — which is handy if your country’s food labels use kilojoules.

How accurate is this?

Calorie formulas are estimates, not measurements. Body composition, hormones, medications, sleep, and non-exercise movement all shift real needs. Treat the result as a well-informed starting point, then let the scale — and how you feel — fine-tune it over a few weeks.