Calorie Deficit Calculator
Calculate how many calories to eat to lose weight. Get your TDEE, choose your deficit level, and see projected fat loss timelines.
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Enter Your Details
Fill in the form to calculate your TDEE and recommended calorie deficit.
Tips for Successful Fat Loss
Don't Go Too Low
Women shouldn't go below 1,200 calories; men shouldn't go below 1,500 without medical supervision. Extreme deficits cause muscle loss and metabolic damage.
Prioritize Protein
Eat 1.6-2.2g protein per kg bodyweight to preserve muscle during fat loss. Protein also keeps you fuller longer.
Lift Weights
Resistance training signals your body to keep muscle. A widely cited rule of thumb is that about a quarter of weight lost by dieting is fat-free mass (muscle, water, and other lean tissue), though it varies (Heymsfield et al., Obesity Reviews 2014).
Take Diet Breaks
Every 8-12 weeks, eat at maintenance for 1-2 weeks. This helps reset hormones and prevents metabolic adaptation.
How Calorie Deficits Work
Calculate TDEE
Your Total Daily Energy Expenditure is how many calories you burn each day. This includes your BMR (base metabolism) plus activity calories.
Create Deficit
Eat less than your TDEE. A 500-calorie deficit means eating 500 calories less than you burn. The old rule of thumb is 3,500 calories per pound, but research shows it overestimates weight loss over time because your energy needs drop as you lose weight.
Lose Fat
Your body makes up the energy difference by burning stored fat. Combined with protein and training, you preserve muscle while losing fat.
Frequently Asked Questions
What is a calorie deficit?
A calorie deficit is eating fewer calories than you burn. This forces your body to use stored fat for energy, causing weight loss.
How big should my calorie deficit be?
A 500-calorie deficit (losing ~0.5kg/1lb per week) is sustainable for most. Larger deficits risk muscle loss and burnout.
Will I lose muscle in a deficit?
Some muscle loss is possible, but you can minimize it with adequate protein, resistance training, and moderate deficit sizes.
Why am I not losing weight?
Common reasons: underestimating calories eaten, overestimating exercise, water retention, or metabolic adaptation from prolonged dieting.
How long should I diet?
8-16 weeks per phase is typical. Take 1-2 week diet breaks eating at maintenance to prevent metabolic adaptation.
Can I lose fat without counting calories?
Yes, but tracking ensures accuracy. Alternatives include portion control, eliminating processed foods, and eating protein-first at meals.
Track Your Progress
Numbers only tell part of the story. PhysiqueAI estimates your body fat and lean mass from photos over time—so you can see whether you're losing fat, not just weight.
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