Free Calorie Deficit Calculator
Calculate exactly how many calories to eat for safe, sustainable weight loss. Get your personalized deficit, daily targets, and timeline to reach your goal weight.
What Is a Calorie Deficit?
A calorie deficit occurs when you consume fewer calories than your body burns. Your body needs a certain number of calories each day to maintain your weight — this is called your Total Daily Energy Expenditure (TDEE). When you eat less than your TDEE, your body must tap into stored energy (primarily fat) to make up the difference.
- TDEE = Calories you burn daily (metabolism + activity)
- Deficit = TDEE − Calories you eat
- Weight loss = Sustained deficit over time
Since ~3,500 calories equals roughly 1 pound of fat, a daily deficit of 500 calories leads to about 1 pound of weight loss per week.
For example: If your TDEE is 2,400 calories and you eat 1,900 calories daily, you have a 500-calorie deficit. Over a week, that's 3,500 calories — approximately one pound of fat loss.
What's a Safe Calorie Deficit?
Not all deficits are created equal. The size of your deficit affects how sustainable your diet is and whether you lose fat or muscle:
| Deficit Size | Weekly Loss | Who It's For | Pros | Cons |
|---|---|---|---|---|
| 250 cal (10-15%) | ~0.5 lb | Already lean, athletes | Preserves muscle, sustainable | Slower progress |
| 500 cal (15-20%) ⭐ | ~1 lb | Most people | Good balance of speed & sustainability | Moderate hunger |
| 750 cal (20-25%) | ~1.5 lb | Higher body fat, short-term | Faster results | Harder to sustain, more hunger |
| 1000 cal (25%+) | ~2 lb | Obese individuals, medical supervision | Rapid initial loss | Muscle loss risk, metabolic adaptation |
The 25% Rule
A general guideline is to never exceed a 25% deficit from your TDEE. Larger deficits become increasingly difficult to sustain and often lead to:
- Increased hunger and cravings
- Muscle loss (especially without adequate protein)
- Fatigue and decreased performance
- Metabolic adaptation (your body burns fewer calories)
- Hormonal disruptions
- Diet "rebounds" and weight regain
How to Calculate Your Calorie Deficit
Calculating your ideal deficit involves three steps:
Step 1: Calculate Your BMR
Your Basal Metabolic Rate (BMR) is the calories your body burns at complete rest. Our calculator uses the Mifflin-St Jeor equation:
Mifflin-St Jeor Equation
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 Step 2: Calculate Your TDEE
Multiply your BMR by an activity factor to get your Total Daily Energy Expenditure:
| Activity Level | Multiplier | Description |
|---|---|---|
| Sedentary | 1.2 | Little to no exercise, desk job |
| Lightly Active | 1.375 | Light exercise 1-3 days/week |
| Moderately Active | 1.55 | Moderate exercise 3-5 days/week |
| Very Active | 1.725 | Hard exercise 6-7 days/week |
| Extremely Active | 1.9 | Physical job + daily training |
Step 3: Subtract Your Deficit
Subtract your chosen deficit from your TDEE:
- 0.5 lb/week: Subtract 250 calories
- 1 lb/week: Subtract 500 calories
- 1.5 lb/week: Subtract 750 calories
- 2 lb/week: Subtract 1,000 calories
Example: A 180 lb man with moderate activity has a TDEE of ~2,700 calories. For 1 lb/week loss: 2,700 - 500 = 2,200 calories daily.
How to Maximize Fat Loss (Not Muscle Loss)
In a deficit, your body doesn't just burn fat — it can also break down muscle for energy. Here's how to preserve muscle while losing fat:
Eat High Protein
Aim for 0.8-1.2g protein per pound of body weight. This is the single most important factor for preserving muscle during weight loss.
Calculate your protein needs →Lift Weights
Resistance training signals your body to keep muscle. Without it, up to 25% of weight lost can be muscle instead of fat.
Moderate Deficit
Keep your deficit at 15-25% of TDEE. Larger deficits increase muscle loss even with high protein.
Prioritize Sleep
Sleep deprivation increases cortisol and shifts weight loss toward muscle rather than fat. Aim for 7-9 hours.
Why You're Not Losing Weight (Even in a Deficit)
If you're confident you're in a deficit but not losing weight, here are the most common culprits:
1. You're Eating More Than You Think
This is the #1 reason. Studies show people underestimate calorie intake by 30-50%. Solutions:
- Weigh your food — Eyeballing portions is notoriously inaccurate
- Track everything — Including oils, sauces, bites, and drinks
- Use verified entries — Database entries can be wrong; cross-check with labels
2. Water Weight Is Masking Fat Loss
Your body holds water based on sodium, carbs, hormones, and stress. You might be losing fat but not seeing scale movement due to:
- High sodium meals
- Menstrual cycle (women can gain 2-6 lbs)
- Starting a new workout routine
- Poor sleep or high stress
Solution: Track weekly weight averages, not daily weigh-ins.
3. Your Deficit Isn't As Large As You Think
Calculators provide estimates. Your actual TDEE may be lower, especially if you:
- Overestimated your activity level
- Have been dieting for a long time (metabolic adaptation)
- Have a naturally slower metabolism
Solution: If not losing after 3 weeks, reduce by another 100-200 calories.
4. Weekend Overeating
A strict week can be undone by weekend indulgences. Two days of eating at maintenance or surplus can erase your deficit:
- 5 days × 500 deficit = 2,500 cal deficit
- 2 days × 500 surplus = 1,000 cal surplus
- Net weekly deficit = only 1,500 calories (0.4 lb/week)
Understanding Metabolic Adaptation
Metabolic adaptation (sometimes called "starvation mode") is a real phenomenon — but it's often misunderstood.
What Actually Happens
When you lose weight and/or restrict calories for extended periods:
- Your smaller body burns fewer calories (this is unavoidable)
- You subconsciously move less (NEAT decreases)
- Your BMR may decrease slightly beyond what weight loss predicts
- Hunger hormones increase
How to Minimize It
- Avoid extreme deficits — Moderate deficits cause less adaptation
- Keep protein high — Preserves metabolism-boosting muscle
- Take diet breaks — Periodic returns to maintenance can help reset hormones
- Stay active — Intentional movement counters NEAT reduction
- Lift weights — Maintains muscle mass and metabolic rate
How Long Should You Stay in a Deficit?
Extended dieting can become counterproductive. Here are general guidelines:
| Diet Phase | Duration | Then Do |
|---|---|---|
| Active deficit | 8-16 weeks | Diet break or maintenance phase |
| Diet break | 1-2 weeks at maintenance | Resume deficit or continue maintenance |
| Maintenance phase | 4-8 weeks | New diet phase if more to lose |
Signs you need a break:
- Constant hunger that doesn't improve
- Sleep problems, irritability, low energy
- Stalled progress despite verified deficit
- Loss of motivation, obsessive food thoughts
- Menstrual irregularities (women)
Frequently Asked Questions
Everything you need to know about calorie deficits
What is a calorie deficit?
A calorie deficit occurs when you consume fewer calories than your body burns (TDEE). This forces your body to use stored energy (fat) for fuel, resulting in weight loss. For example, if your TDEE is 2,500 calories and you eat 2,000 calories, you have a 500-calorie deficit.
How big should my calorie deficit be for weight loss?
A moderate deficit of 500 calories per day is recommended for most people, resulting in about 1 pound of weight loss per week. Larger deficits (750-1000 calories) can work short-term but are harder to sustain and may lead to muscle loss. Never go below a 25% deficit from your TDEE.
Is a 1000 calorie deficit safe?
A 1000-calorie deficit can be safe for people with higher body fat, but it's aggressive and may not be sustainable long-term. It can lead to increased hunger, fatigue, muscle loss, and metabolic adaptation. Most experts recommend a 500-750 calorie deficit for sustainable results.
How do I calculate my calorie deficit?
First, calculate your TDEE (Total Daily Energy Expenditure) using your BMR and activity level. Then subtract your desired deficit (typically 500 calories for 1 lb/week loss). For example: TDEE of 2,400 - 500 deficit = 1,900 daily calories for weight loss.
Why am I not losing weight in a calorie deficit?
Common reasons include: underestimating food intake, overestimating exercise calories, water retention masking fat loss, metabolic adaptation from prolonged dieting, or your deficit isn't as large as you think. Track food accurately with a scale for 2-3 weeks to verify your actual intake.
What's the minimum calories I should eat?
General guidelines suggest women shouldn't go below 1,200 calories and men below 1,500 calories without medical supervision. More importantly, don't go below your BMR for extended periods. Eating too little causes muscle loss, nutrient deficiencies, and metabolic slowdown.
How long does it take to see weight loss results?
With a 500-calorie daily deficit, expect to lose about 1 pound per week. You may see faster results in the first 1-2 weeks due to water weight loss. Visible changes typically appear after 4-8 weeks. Focus on weekly weight averages, not daily fluctuations.
Should I eat back exercise calories?
Generally no. Your activity level in the calculator already accounts for exercise. Eating back exercise calories often leads to overestimating burn and slower results. If you're extremely active and always hungry, slightly increase your activity level setting instead.
Will a calorie deficit slow my metabolism?
Mild metabolic adaptation is normal with weight loss — your smaller body burns fewer calories. Severe metabolic slowdown happens with extreme deficits over long periods. Prevent this by keeping deficits moderate (15-25% of TDEE), eating adequate protein, and taking periodic diet breaks.
How often should I adjust my calorie deficit?
Recalculate every 10-15 pounds of weight loss, or every 4-6 weeks if progress stalls. As you lose weight, your TDEE decreases, meaning your deficit shrinks. You may need to reduce calories slightly or increase activity to maintain the same rate of loss.
References
- Mifflin MD, St Jeor ST, et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990;51(2):241-247. PubMed
- Hall KD, et al. Quantification of the effect of energy imbalance on bodyweight. Lancet. 2011;378(9793):826-837. PubMed
- Trexler ET, Smith-Ryan AE, Norton LE. Metabolic adaptation to weight loss: implications for the athlete. J Int Soc Sports Nutr. 2014;11(1):7. PubMed
- Helms ER, Aragon AA, Fitschen PJ. Evidence-based recommendations for natural bodybuilding contest preparation. J Int Soc Sports Nutr. 2014;11:20. PubMed