Daily calorie estimate
- The NHS suggests that eating about 600 kcal a day less than you burn leads to a loss of around 0.5–1 kg a week for most people.
- Your result is an estimate: treat it as a starting point and adjust based on how your weight changes over two to three weeks.
- Very low-calorie diets (below about 800 kcal a day) should only be followed with medical supervision.
How the estimate works
The calculator first estimates your basal metabolic rate (BMR) — the energy your body needs at rest to breathe, circulate blood and keep warm — using the Mifflin–St Jeor equation, which is one of the more accurate formulas for adults. It then multiplies this by an activity factor to estimate the calories you burn on a typical day. Eating that amount keeps your weight stable; eating a little less leads to gradual weight loss.
Making a deficit you can keep
- Build meals around protein and fibre. Both keep you fuller for longer. See our nutrition guide.
- Watch drinks. Sugary drinks, large coffees and alcohol add up quickly — alcohol has 7 kcal per gram, almost as much as fat.
- Fill half your plate with vegetables. They add volume for very few calories.
- Keep active. Movement protects muscle and makes the deficit easier. Strength training matters most.
Why weight loss slows
As you lose weight, your body needs less energy, so the same intake creates a smaller deficit. Re-run the calculator every 5 kg or so. Short plateaus are normal; if progress has stopped for more than a month, look at portion sizes, drinks and weekend eating before cutting further.
When calorie counting isn’t enough
For many people, appetite, hormones and genetics make a lasting deficit very hard, however disciplined they are. If you have a BMI of 30 or more, or 27 or more with a weight-related condition, a medical weight-loss consultation can look at what else may help.
Not sure if medical weight loss is right for you?
Our free online assessment takes about five minutes. A GPhC-registered prescriber reviews it and only recommends treatment if it is safe and suitable for you.
Start the free assessmentFrequently asked questions
Do I need to count calories to lose weight?
No. Calorie counting suits some people, but many lose weight by changing what and when they eat — more protein and vegetables, fewer sugary drinks and snacks — without tracking every number.
Is 1,200 calories a day safe?
It can be appropriate for some women for a period, but it is low for many people, especially if you are active. Going much lower risks missing nutrients and losing muscle. Speak to your GP or a dietitian before following a very low-calorie plan.
Why has my weight loss stopped?
Your energy needs fall as you lose weight, and water retention can hide fat loss for a week or two. Recalculate your needs, check portion sizes and drinks, and keep up strength training before cutting calories further.
This page is general health information. It does not replace advice from your GP or another healthcare professional who knows your history. If you have symptoms that worry you, contact your GP or NHS 111; in an emergency call 999. Prescription treatment is only supplied after an assessment by a registered prescriber.