Calorie Deficit Calculator
Calculate the exact calorie deficit you need for weight loss. See your daily calorie target, projected timeline to reach your goal weight, and a week-by-week weight loss forecast.
A calorie deficit occurs when you consume fewer calories than your body burns (your TDEE). A deficit of 500 calories per day produces approximately 1 pound of fat loss per week. A deficit of 250 calories per day produces 0.5 pounds per week — slower but more sustainable and muscle-sparing.
Weekly Fat Loss ≈ Deficit × 7 / 3,500 lbs
Time to Goal = Weight to Lose / Weekly Loss Rate
Enter Your Details
Your Calorie Deficit Plan
Recommended Macro Split for Fat Loss
Weight Loss Timeline
| Week | Weight (lbs) | Lost (lbs) | Daily Calories | BMI |
|---|
How This Calorie Deficit Calculator Works
This calculator first estimates your Total Daily Energy Expenditure (TDEE) using the Mifflin-St Jeor equation — which the American Dietetic Association considers the most accurate for healthy adults — multiplied by your activity level. It then subtracts your chosen deficit to produce a daily calorie target. The timeline projection assumes a constant deficit, though in practice your TDEE will decrease slightly as you lose weight (which is why the projection table adjusts calories downward every 4 weeks).
Understanding the 3,500-Calorie Rule
The widely cited rule that 3,500 calories equals one pound of fat is a simplification. The original research by Max Wishnofsky (1958) established this approximation, and it remains useful for short-term planning. However, over longer periods, metabolic adaptation means your body becomes more efficient, so the actual rate of loss slows over time. This calculator accounts for this by recalculating TDEE as your weight decreases.
For a more precise baseline, calculate your resting metabolic rate with our BMR Calculator, then factor in activity with the TDEE Calculator. The difference between your TDEE and this calculator is that TDEE shows your maintenance calories, while this tool shows the deficit target and projects outcomes over time.
Choosing the Right Deficit Size
250 cal/day (0.5 lb/week): Most sustainable. Best for people within 10-15 lbs of their goal or those who want to maximize muscle retention. Almost no metabolic adaptation at this level. Recommended for active individuals who are already lean.
500 cal/day (1 lb/week): The "gold standard" deficit recommended by most dietitians. Produces meaningful progress without excessive hunger or muscle loss when combined with adequate protein intake (1.4-1.6g/kg) and resistance training.
750 cal/day (1.5 lb/week): Appropriate for individuals with significant weight to lose (30+ lbs). Requires careful attention to nutrition quality and protein intake to prevent excessive lean mass loss.
1,000 cal/day (2 lb/week): The maximum recommended rate. Should not reduce daily intake below 1,200 calories for women or 1,500 for men. Risk of muscle loss increases significantly — essential to prioritize strength training (track with One Rep Max Calculator) and high protein.
Protecting Muscle During a Deficit
The three most important factors for preserving lean mass during weight loss are protein intake, resistance training, and deficit size. Research from McMaster University found that consuming 2.4g/kg of protein during a deficit preserved significantly more lean mass than 1.2g/kg, even at aggressive deficit levels. Calculate your specific needs with the Protein Intake Calculator and split into optimal ratios with the Macro Calculator.
Monitor your body composition with the Body Fat Calculator and Lean Body Mass Calculator every 2-4 weeks. If lean mass is declining faster than expected, reduce the deficit and increase protein. Track your strength with the One Rep Max Calculator — maintaining or increasing your lifts during a cut is the best real-world indicator that you're preserving muscle.
When to Take Diet Breaks
Research from the University of Tasmania (the MATADOR study) found that participants who took 2-week diet breaks every 2 weeks of dieting lost more fat and retained more muscle than those who dieted continuously. Periodic refeeds at maintenance calories (your TDEE) help reset hormones like leptin and ghrelin, reduce metabolic adaptation, and improve long-term adherence.
Consider scheduling 1-2 refeed days per week at maintenance calories, or taking a full diet break (7-14 days at TDEE) every 6-12 weeks of continuous deficit. This extends your timeline slightly but produces better body composition outcomes.
Deficit Size Reference
| Daily Deficit | Weekly Loss | Monthly Loss | Best For | Risk Level |
|---|---|---|---|---|
| 250 cal | 0.5 lb | 2 lbs | Near goal weight, lean individuals | Low |
| 500 cal | 1 lb | 4 lbs | Most people (recommended) | Low |
| 750 cal | 1.5 lbs | 6 lbs | Significant weight to lose (30+ lbs) | Moderate |
| 1,000 cal | 2 lbs | 8 lbs | Medically supervised, very overweight | Higher |
Frequently Asked Questions
Explore More Tools
Start with your TDEE Calculator for baseline maintenance calories. Split deficit calories into optimal ratios with the Macro Calculator. Ensure adequate protein for muscle preservation. Track exercise contribution with the Calories Burned Calculator. Monitor your progress with BMI, Body Fat, and Lean Body Mass. Stay hydrated with the Water Intake Calculator — dehydration masks fat loss on the scale. Prioritize sleep — research shows sleep-deprived dieters lose 55% more muscle.
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