Calorie Calculator UK
Calculate your daily calorie needs using the Mifflin-St Jeor equation — endorsed by the British Dietetic Association (BDA) and referenced in NICE obesity guidelines as the most accurate formula for estimating Basal Metabolic Rate (BMR).
Enter Your Details
Suggested Daily Macros
About the Mifflin-St Jeor Formula
| Activity Level | Multiplier | Example |
|---|---|---|
| Sedentary | ×1.2 | Desk job, no structured exercise |
| Lightly active | ×1.375 | Walking, light gym 1–3 days/week |
| Moderately active | ×1.55 | Moderate cardio or weights 3–5 days/week |
| Very active | ×1.725 | Hard training 6–7 days/week |
| Extra active | ×1.9 | Physical job + daily training |
Source: Mifflin MD, et al. (1990) A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. Endorsed by the British Dietetic Association (BDA) and referenced in NICE obesity pathway (NG246).
This calculator provides an estimate only. Individual calorie needs vary based on muscle mass, metabolic conditions, medications, and other factors. The macro split is a general guideline — consult a registered dietitian for personalised nutrition advice. Do not follow a very low calorie diet (<800 kcal/day) without medical supervision. Not suitable for children, pregnant or breastfeeding women. If you or someone you know is struggling with disordered eating, contact the BEAT eating disorders helpline on 0808 801 0677 or your GP.
Clinically reviewed by Tahir Hameed, Pharmacist Independent Prescriber (GPhC: 2210908) — Last reviewed: April 2026
Frequently Asked Questions
How many calories should I eat per day UK?
The NHS general guideline is approximately 2,500 kcal/day for men and 2,000 kcal/day for women to maintain weight. However, your actual needs depend on age, height, weight, and activity level — which is exactly what this calculator estimates using the Mifflin-St Jeor equation.
What is the Mifflin-St Jeor equation?
The Mifflin-St Jeor equation (1990) is considered the most accurate formula for estimating Basal Metabolic Rate (BMR) in healthy adults. It is endorsed by the British Dietetic Association (BDA) and referenced in NICE obesity guidelines. The formula calculates your resting calorie burn, which is then multiplied by an activity factor to give your Total Daily Energy Expenditure (TDEE).
What is the difference between BMR and TDEE?
BMR (Basal Metabolic Rate) is the number of calories your body burns at complete rest — just to keep you alive (breathing, circulation, cell repair). TDEE (Total Daily Energy Expenditure) is your BMR multiplied by an activity factor that accounts for daily movement, exercise, and physical activity. TDEE is the number you should use for meal planning.
Is it safe to eat fewer than 1,200 calories a day?
Very low calorie diets (VLCDs) below 800 kcal/day should only be followed under medical supervision, according to NICE guidelines. Diets between 800–1,200 kcal/day can be effective for short-term weight loss but may lack essential nutrients. The NHS recommends a sustainable deficit of 500–600 kcal/day below your TDEE for safe weight loss of 0.5–1 kg per week.
Does this calculator store my personal data?
No. All calculations are performed entirely in your browser using JavaScript. Your age, weight, height, and calorie results are never sent to any server, stored in any database, or shared with any third party.