Calorie Deficit Calculator — Daily Target & Goal Timeline
Calculate the daily calorie target needed to reach your weight goal by your chosen timeline. Uses the Mifflin-St Jeor equation to estimate your TDEE, then projects how long your plan will take.
| Checkpoint | Projected weight | Total lost |
|---|---|---|
| Week 1 | 184.0 lbs | −1.0 lbs |
| Week 4 | 181.0 lbs | −4.0 lbs |
| Week 8 | 177.0 lbs | −8.0 lbs |
| Week 12 | 173.0 lbs | −12.0 lbs |
Most research supports a deficit of 300–750 cal/day for sustainable fat loss while preserving lean mass. Pair with 0.7–1g protein per pound of body weight and resistance training for best results.
How to use this calculator
Enter your current weight, goal weight, height, age, gender, and activity level. Then choose your preferred rate of loss — Moderate (−500 cal/day) is the most sustainable for most people. Your daily calorie target, deficit, and estimated goal date update instantly. Use the Custom option to dial in an exact deficit. Toggle between Imperial and Metric using the button above.
Understanding your calorie deficit results
Your TDEE (Total Daily Energy Expenditure) is the estimated number of calories your body burns each day. Eating below your TDEE creates a deficit — stored fat is burned to make up the gap. One pound of fat contains approximately 3,500 calories, so a 500 cal/day deficit produces roughly 1 lb/week of fat loss. Actual results vary based on adherence, water retention, hormonal factors, and metabolic adaptation.
Frequently asked questions
Weight loss rate by calorie deficit
One pound of fat contains approximately 3,500 calories. Creating a consistent daily deficit is the most reliable path to fat loss. Larger deficits produce faster results but carry higher risks.
| Daily deficit | Fat loss per week | Weeks to lose 20 lbs | Risk level |
|---|---|---|---|
| 250 cal/day | ~0.5 lbs | ~40 weeks | Low — sustainable, muscle-sparing |
| 500 cal/day | ~1 lb | ~20 weeks | Low-moderate — widely recommended |
| 750 cal/day | ~1.5 lbs | ~13 weeks | Moderate — manageable for most |
| 1000 cal/day | ~2 lbs | ~10 weeks | Moderate-high — requires careful nutrition |
| 1200+ cal/day | ~2.5+ lbs | <8 weeks | High — significant muscle loss risk |
Mifflin-St Jeor formula (used in this calculator)
The Mifflin-St Jeor equation is the most validated formula for estimating basal metabolic rate (BMR) in adults. It was developed in 1990 and is preferred over the older Harris-Benedict equation for most populations.
| Sex | Formula |
|---|---|
| Men | BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5 |
| Women | BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161 |
Why slow cuts preserve muscle
The rate of your calorie deficit directly impacts how much lean mass you retain. Aggressive cuts sacrifice both fat and muscle, while gradual deficits allow your body to preferentially burn stored fat.
- ·Muscle protein synthesis requires adequate calories — large deficits suppress anabolic signaling
- ·Cortisol (stress hormone) rises with aggressive restriction, breaking down muscle tissue for energy
- ·Protein intake becomes critically important during a cut — aim for 0.7–1g per pound of body weight
- ·A slower cut allows you to continue training with adequate intensity and volume, further preserving muscle
- ·Rapid weight loss often includes significant water and glycogen loss that mimics fat loss — creating false progress readings
- ·Most research supports a maximum deficit of 500–750 calories/day for good muscle retention in non-obese individuals
Diet breaks, refeeds, and metabolic adaptation
Sustained caloric deficits trigger adaptive responses that slow fat loss — commonly called metabolic adaptation or "starvation mode." Strategic refeeds and diet breaks counteract this.
- ·Metabolic adaptation: after weeks of restriction, TDEE can drop 10–15% below predicted — the body becomes more fuel-efficient
- ·Leptin, the hunger-suppressing hormone, falls during prolonged deficits, increasing appetite and reducing motivation
- ·A refeed day (one day at maintenance calories) can temporarily restore leptin levels and improve adherence
- ·A diet break (1–2 weeks at maintenance) after every 6–12 weeks of dieting helps reset metabolic rate and reduce psychological fatigue
- ·Weight loss plateaus often signal metabolic adaptation rather than adherence failure — reducing the deficit further or taking a break can restart progress