Calorie Deficit Calculator
Find your maintenance calories, a realistic fat-loss target and how much protein to eat. Takes 20 seconds.
How this calculator works
It uses the Mifflin-St Jeor equation, one of the most accurate everyday formulas for resting calories, then multiplies by your activity level to estimate maintenance (TDEE). The fat-loss target takes 10–25% off maintenance, never going below 1,200 kcal (women) or 1,500 kcal (men). Protein is set at 1.6–2.2g per kg of bodyweight, the range research supports for keeping muscle while dieting.
FAQ
How big should my calorie deficit be?
For most people, 15–20% below maintenance (often 300–600 kcal a day) gives steady fat loss of about 0.3–0.7 kg per week without wrecking energy or training.
Why am I not losing weight on my deficit?
Daily weight bounces with water, salt and carbs. Track your weekly average for 2–3 weeks. If it's flat, lower calories by 100–150 or add 2,000 more steps a day.
Do I need to count calories forever?
No. Count for a few weeks to learn portions, then switch to simple habits like protein first, half a plate of veg and fewer liquid calories.
Estimates only, based on standard formulas. Not medical advice. If you have a medical condition, are pregnant, or are under 18, talk to your GP first.