Calorie Calculator
Find out how many calories you need in a day to maintain your weight — then what to eat to lose or gain at a rate you can actually keep up.
Fill in the fields to see your result.
How the number is worked out
It happens in three steps, and each one is simple on its own.
- Your BMR — the calories you'd burn lying completely still all day. This page uses the Mifflin-St Jeor equation, the one most dietitians reach for.
- Multiply by activity to get your total daily energy expenditure, or TDEE. That's your maintenance level: eat this and your weight holds steady.
- Add or subtract for your goal. A deficit loses weight, a surplus gains it, and the size of the gap sets the speed.
Choosing your activity level honestly
| Level | Multiplier | What it actually means |
|---|---|---|
| Sedentary | × 1.2 | Desk job, no real exercise |
| Light | × 1.375 | Desk job plus 1–3 sessions a week |
| Moderate | × 1.55 | Training 4–5 times a week |
| Very active | × 1.725 | Hard training 6–7 times a week |
| Extra active | × 1.9 | Manual job, or training twice a day |
This is where most people go wrong. Overstating your activity by one tier can add three or four hundred calories to your target, which is enough to cancel a deficit entirely. If you're hovering between two levels, take the lower one — you can always adjust upward once you see what your weight actually does.
Losing weight at a sensible rate
Roughly 7,700 calories is stored in a kilogram of body fat, or about 3,500 in a pound. That's where the standard advice comes from:
- 500 fewer calories a day ≈ half a kilo, or one pound, a week
- 1,000 fewer calories a day ≈ one kilo, or two pounds, a week
Faster than that is generally not advisable without medical supervision. And the rule is an approximation, not physics — you lose water and glycogen alongside fat, and your metabolic rate drifts down as you get lighter. Expect the first fortnight to move faster than predicted and the following months to move slower.
Why there's a floor
If the maths for your chosen goal produces a very low number, this calculator shows a floor instead and tells you it has done so. Harvard Health Publications puts that floor at around 1,200 calories a day for women and 1,500 for men outside medical supervision.
Below those levels it becomes genuinely difficult to get enough protein, vitamins and minerals, and the approach tends to defeat itself — energy drops, training suffers, muscle goes along with the fat, and it becomes very hard to sustain. If you want to lose faster than the floor allows, the answer is more activity rather than less food, or a conversation with a doctor.
Frequently asked questions
How many calories should I eat to lose weight?
A deficit of about 500 calories a day works out at roughly half a kilo, or one pound, of fat a week. That's the rate most guidance settles on because it's fast enough to see progress and slow enough to stick to. Doubling it to 1,000 a day for a kilo a week is possible but much harder to sustain, and it gets riskier the leaner you already are. Losing more than about a kilo a week is generally not advisable without medical supervision.
Why does the calculator refuse to go below a certain number?
Because very low intakes make it difficult to get enough protein, vitamins and minerals, and they tend to backfire. Harvard Health Publications gives a floor of around 1,200 calories a day for women and 1,500 for men outside medical supervision. If the maths for your chosen goal drops under that, this calculator shows the floor instead and tells you — rather than quietly handing you a number you shouldn't be eating at.
Is the 3,500 calories per pound rule accurate?
It's a useful approximation and it's where the 500-a-day advice comes from, but it's not a law of physics. It assumes the weight lost is pure fat, and in reality you also lose water, glycogen and some muscle, especially early on. Metabolic rate also drifts down as you get lighter. Expect the first week or two to show more movement than the formula predicts, and the later weeks to show less.
Which activity level should I pick?
Be honest and, if you're torn between two, pick the lower one. Most people overestimate how active they are — a desk job with three gym sessions a week is "light" to "moderate", not "very active". The "extra active" tier is for manual labour or training twice a day, not for someone who runs at weekends. Picking too high is the single most common reason a calorie target doesn't work.
Do I need to count calories to lose weight?
No, though it helps some people because it makes the invisible visible. What matters is being in a deficit consistently, and there are other routes to that — changing portion sizes, cutting liquid calories, eating more protein and fibre so you're fuller. Use this number as a target if counting suits you, or just as a reference point for how much you're working with.
Are my numbers sent anywhere?
No. Everything is worked out inside your own browser. Nothing you type is uploaded, stored or shared, and there's no sign-up.
Please note: CalcuLane gives estimates for general information only and is not medical advice, a diagnosis or a treatment plan. Calorie needs vary considerably between individuals and these equations describe population averages. BMR uses the Mifflin-St Jeor equation (1990). Do not follow a very low calorie intake without medical supervision, and speak to a doctor or registered dietitian before making significant changes to what you eat.