Use this independent UK calorie deficit calculator to estimate your resting energy needs, maintenance calories and a daily calorie target for weight loss. It is not an official NHS calculator. The NHS advises that people trying to lose weight can aim to reduce their current intake by around 600 kcal a day, while individual energy needs vary.

What is a calorie deficit?

A calorie deficit means your energy intake is lower than your energy expenditure. NICE recommends that dietary approaches for adults managing overweight or obesity keep total energy intake below energy expenditure and remain nutritionally balanced.

How this calculator works

The calculator first estimates basal metabolic rate (BMR) with the Mifflin-St Jeor equation. It then multiplies BMR by the selected activity factor to estimate total daily energy expenditure (TDEE). Your selected calorie deficit is subtracted from TDEE to produce an estimated daily target.

Men: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5.

Women: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161.

Estimated target = TDEE − selected daily deficit.

Why 600 calories is shown

NHS Better Health says that people trying to lose weight can aim to reduce their intake by around 600 calories a day. This is general guidance, not a personalised prescription. The calculator therefore defaults to 600 kcal but lets you compare other moderate deficits.

Worked example

For a 35-year-old woman who weighs 75 kg, is 165 cm tall and selects lightly active, the equation estimates BMR first, then applies the activity factor to estimate maintenance calories. Selecting a 600 kcal deficit subtracts 600 from that estimated maintenance figure. Real-world needs and weight change can differ from the estimate.

Important limitations

• TDEE is an estimate rather than a direct measurement.
• Do not use this calculator for children or during pregnancy.
• If you have an eating disorder or disordered eating, diabetes, another medical condition, or take medicines affecting weight or appetite, seek professional advice.
• NICE says 800–1,200 kcal/day low-energy diets should only be considered within specialist, supported weight-management strategies for specified groups; very-low-energy diets below 800 kcal/day also require specialist services and supervision.

Authoritative sources

• NHS Better Health: calories and weight loss
• NICE NG246: physical activity and diet
• Mifflin MD et al. (1990), A new predictive equation for resting energy expenditure in healthy individuals.

Related calculators

• TDEE Calculator NHS
• BMI Calculator NHS
• Weight Loss Calculator NHS
• BMR Calculator NHS
• Calorie Calculator NHS

Frequently asked questions

Is this an official NHS calorie deficit calculator?

No. This is an independent calculator that references NHS and NICE guidance. It is not operated or endorsed by the NHS.

Does the NHS recommend a 600 calorie deficit?

NHS Better Health currently advises aiming to reduce intake by around 600 calories a day for weight loss. Individual needs differ, so treat this as general guidance.

Is my calculated target guaranteed to cause a specific amount of weight loss?

No. Energy equations and activity factors are estimates, and actual weight change varies between people and over time.

Should I eat below my BMR?

BMR is an estimate of resting energy expenditure, not a personalised minimum intake. Very restrictive diets should not be planned from a calculator alone. NICE places low-energy diets within specialist supported programmes for specific groups.

Independent informational tool only. Not affiliated with or endorsed by the NHS. This calculator does not provide medical advice.