Free UK Calorie Deficit Calculator 2025. Calculate your safe daily calorie target for weight loss based on NHS guidelines.
Calculate your safe daily calorie target for healthy, sustainable weight loss based on NHS guidelines.
A calorie deficit is the foundation of all successful weight loss. It occurs when you consume fewer calories than your body uses for energy. When in a deficit, your body taps into stored energy (primarily body fat) to make up the difference, resulting in weight loss.
The science is straightforward: approximately 7,700 calories equals 1kg of body fat. To lose 0.5kg per week, you need a daily deficit of approximately 500 calories. This deficit can be achieved through eating less, moving more, or ideally a combination of both.
| Deficit Type | Daily Deficit | Weekly Loss | Best For | Sustainability |
|---|---|---|---|---|
| Conservative | 250 calories | ~0.25kg | Athletes, those near goal weight | Very High |
| Moderate | 500 calories | ~0.5kg | Most adults (NHS recommended) | High |
| Aggressive | 750 calories | ~0.75kg | Those with more to lose, time-limited | Moderate |
| Very Aggressive | 1,000 calories | ~1kg | Medically supervised, obese individuals | Low |
There's a floor to how low your calories should go, regardless of how quickly you want to lose weight. Going too low risks nutrient deficiencies, muscle loss, and metabolic damage.
| Category | Minimum Calories/Day | Notes |
|---|---|---|
| Women | 1,200 calories | NHS minimum for adequate nutrition |
| Men | 1,500 calories | NHS minimum for adequate nutrition |
| Very Low Calorie Diet | 800-1,200 calories | Only under medical supervision |
Use a food scale and apps like MyFitnessPal or Nutracheck. Most people underestimate intake by 20-50%. Weigh food raw before cooking for accuracy.
Aim for 1.6-2.2g per kg bodyweight. Protein preserves muscle, keeps you fuller longer, and has a higher thermic effect (burns more calories to digest).
Fill up on low-calorie, high-volume foods like vegetables, salads, and broth-based soups. You can eat more food while staying in deficit.
One high-calorie day won't ruin progress. What matters is your weekly average. Get back on track the next meal, not "next Monday".
Exercise creates additional deficit and preserves muscle. Even 8,000-10,000 daily steps can burn 300-500 extra calories.
Poor sleep increases hunger hormones (ghrelin) and reduces leptin. Aim for 7-9 hours. Sleep deprivation can add 300+ calories to daily intake.
Cutting too many calories too quickly leads to extreme hunger, low energy, and inevitable binges. Start with a moderate deficit and adjust based on progress.
That splash of milk in tea, the handful of crisps, the finishing of kids' leftovers - these untracked calories add up. In the UK, an estimated 400+ calories daily go untracked.
Fitness trackers and gym machines often overestimate calories burned by 20-50%. Don't "eat back" all your exercise calories - use half at most.
A strict 1,500-calorie week can be undone by a 4,000-calorie Saturday. This creates a net weekly surplus. Allow flexibility, but track weekends too.
Your weight can fluctuate 1-2kg daily due to water, sodium, carbs, and digestion. Judge progress by weekly averages, not daily weigh-ins.
A calorie deficit occurs when you consume fewer calories than your body burns (TDEE). For example, if your TDEE is 2,000 calories and you eat 1,500, you're in a 500-calorie deficit. This forces your body to use stored fat for energy, resulting in weight loss. The size of the deficit determines how quickly you lose weight - approximately 7,700 calories equals 1kg of body fat.
The NHS recommends a deficit of 500-600 calories per day for safe weight loss of 0.5-1kg per week. Very low calorie diets (under 1,200 for women or 1,500 for men) should only be followed under medical supervision. Larger deficits increase risk of muscle loss, nutrient deficiencies, gallstones, and metabolic adaptation.
Most adults in the UK can safely lose weight eating 1,400-1,800 calories per day, depending on their current weight, height, age, gender, and activity level. As a general guide, women typically aim for 1,200-1,400 calories and men 1,500-1,800 for moderate weight loss. However, very active individuals may need more. Use this calculator to get a personalised recommendation.
Common reasons include: underestimating calories consumed (not weighing food accurately), overestimating exercise calories burned, water retention masking fat loss (especially after high-sodium meals or around menstruation), metabolic adaptation from prolonged dieting, or medical conditions like hypothyroidism. Track accurately for 2-3 weeks; if still no progress, consult your GP.
Diet breaks are recommended every 8-12 weeks of continuous dieting. These 1-2 week periods at maintenance calories help restore hormones and prevent metabolic slowdown. After reaching your goal, gradually increase calories by 100-200 per week (reverse dieting) to find your new maintenance level without rapid weight regain.
Muscle loss can occur if the deficit is too aggressive, protein intake is insufficient, or resistance training is neglected. To preserve muscle while losing fat: keep deficits moderate (500 cal max), consume 1.6-2.2g protein per kg bodyweight, maintain strength training 2-4x weekly, and don't lose weight too quickly (0.5-1kg per week maximum).
Generally, no - or only partially. Fitness trackers and gym machines often overestimate calories burned by 20-50%. If you feel you need to eat back some exercise calories (especially after intense workouts), eat back no more than half. Your activity level is already factored into your TDEE calculation, so additional adjustments may cause you to overeat.
BMR (Basal Metabolic Rate) is the calories your body burns at complete rest - just to keep you alive (breathing, circulation, organ function). TDEE (Total Daily Energy Expenditure) includes your BMR plus all activities: walking, exercise, digestion, and even fidgeting. Your TDEE is what you subtract from to create a calorie deficit.
Last updated: December 2025 | Reviewed for accuracy against current NHS guidelines
Expert Reviewed — This calculator is reviewed by our team of financial experts and updated regularly with the latest UK tax rates and regulations. Last verified: January 2026.
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