Health Hub · Free tool
Calorie Calculator
Work out how many calories you actually need each day: your BMR, your maintenance calories (TDEE), and realistic targets for losing or gaining weight — using the same equation dietitians use.
Note: your weight-loss figure has been capped at a sensible minimum. Prolonged very-low-calorie eating needs medical supervision — please involve your GP.
How this calorie calculator works
It uses the Mifflin-St Jeor equation — the formula research dietitians rate as the most accurate for estimating metabolism from height, weight, age and sex — then multiplies by an activity factor to estimate your total daily energy expenditure. No fad maths, the same method behind most clinical calculators.
BMR: your basal metabolic rate
Your BMR is the energy your body burns doing nothing at all — keeping your heart beating, lungs breathing, brain thinking and body warm. For most people it's 1,200–2,000 calories a day and makes up 60–75% of everything you burn. This is why "eat less, move more" undersells the picture: most of your burning happens before you take a single step.
TDEE: your maintenance calories
Total daily energy expenditure (TDEE) is your BMR plus everything else — walking, working, fidgeting, digesting and exercise. It's the number that actually matters day to day: eat around your TDEE and your weight holds steady; eat consistently below it and you lose; above it and you gain. The activity multipliers this calculator uses:
| Lifestyle | Multiplier | Looks like |
|---|---|---|
| Mostly sitting | ×1.2 | Desk work, driving, little planned exercise |
| Lightly active | ×1.375 | Exercise 1–3 days a week, some walking |
| Moderately active | ×1.55 | Exercise 3–5 days a week or an active job |
| Very active | ×1.725 | Hard exercise most days |
| Extremely active | ×1.9 | Physical job plus daily training |
Most people overestimate their activity level by one notch. If your results haven't matched reality before, try the honest option down.
How many calories should I eat a day?
The UK reference intakes — 2,000 calories a day for women, 2,500 for men — are population averages, useful for reading food labels but blunt for individuals. A 1.55m sedentary woman and a 1.9m active man need very different amounts, which is exactly what this calculator personalises. Your TDEE is a far better anchor than the label figure.
The calorie deficit, explained honestly
Half a kilogram of body fat stores roughly 3,500 calories, so eating about 500 calories under your TDEE each day produces around 0.5kg (1lb) of loss a week — the pace NHS guidance calls sensible and sustainable. Two honest caveats:
- The number moves. As you lose weight your TDEE falls, so recalculate every few kilograms rather than riding one figure for months.
- Adherence beats aggression. A 250-calorie deficit you keep for six months beats an 800-calorie deficit you abandon in three weeks. Slower is usually faster.
Protein and fibre are the dieter's allies — they keep you full on fewer calories. Crash diets under 1,200–1,500 calories cost muscle as well as fat and rarely hold; if that's the territory you feel you need, involve your GP first.
Who this calculator isn't for
- Under-18s — growing bodies have different needs; this tool is calibrated for adults.
- Pregnancy and breastfeeding — energy needs change by trimester; your midwife is the right guide.
- Anyone with a history of disordered eating — calorie counting can do more harm than good; please put support first. The NHS and Beat (0808 801 0677) can help.
Put the numbers to work
Start with your BMI result to see whether changing weight is even worth your effort, browse our Health Advice for the habits that make deficits liveable — sleep in particular is the quiet saboteur of weight loss — and if medicines, supplements or anything else on the pharmacy shelf could help or hinder, our pharmacist is a message away.
Frequently asked questions
Is this a TDEE calculator or a BMR calculator?
Both: it calculates your BMR with Mifflin-St Jeor, then applies your activity level to give TDEE — your maintenance calories — plus deficit and surplus targets built from it.
How accurate are the numbers?
Within roughly 10% for most adults — good enough to plan with. Treat your figure as a starting point: hold it for three weeks, watch the scales, and adjust by 100–200 calories if reality disagrees.
Do I need to hit the number exactly every day?
No. Your weekly average is what your body notices — a heavier Saturday balanced by lighter weekdays works exactly as well as robotic consistency, and it's far easier to live with.