How to Calculate Your Calorie Deficit for Weight Loss
Every sustainable fat loss approach involves eating fewer calories than you burn. But the size of that deficit — and how you create it — determines whether you lose mostly fat or also sacrifice muscle, energy, and metabolism. Here's the full calculation, explained clearly.
Find your exact calorie deficit target
Our calorie deficit calculator computes your TDEE and recommends a deficit based on your weight loss goal.
Step 1 — Calculate your TDEE
Your Total Daily Energy Expenditure (TDEE) is the total number of calories your body burns per day, accounting for your basal metabolic rate (BMR) plus all activity. It's the number you need to eat below to lose weight.
TDEE is calculated in two steps:
Step 1a — BMR. Your basal metabolic rate is the calories burned at complete rest. The most accurate formula for most people is the 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
Example: 35-year-old woman, 65 kg, 165 cm → BMR = 650 + 1031 − 175 − 161 = 1,345 kcal/day
Step 1b — Activity multiplier. Multiply your BMR by your activity level:
| Activity Level | Multiplier | Description |
|---|---|---|
| Sedentary | 1.2 | Desk job, little or no exercise |
| 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 |
| Extra active | 1.9 | Physical job + hard training |
Continuing the example: TDEE = 1,345 × 1.375 (lightly active) = 1,849 kcal/day. This is the maintenance level — eating this amount results in no weight change.
Step 2 — Choose your deficit size
A deficit of 3,500 calories roughly equals one pound of fat loss. This means a daily deficit of 500 calories produces approximately 1 lb/week of fat loss — the most commonly cited rate for sustainable progress.
In practice, the relationship isn't perfectly linear because your body adapts over time, and early weight loss includes water weight. But it's a reliable planning framework.
| Deficit Type | Daily Deficit | Expected Loss | Best For |
|---|---|---|---|
| Gradual | 250 cal/day | ~0.5 lb/week | Minimizing muscle loss, long-term compliance |
| Moderate | 500 cal/day | ~1 lb/week | Most people — sustainable and effective |
| Aggressive | 750 cal/day | ~1.5 lb/week | Short-term, with higher protein intake |
| Very aggressive | 1,000 cal/day | ~2 lb/week | Only with medical supervision |
⚠ Safety floor
Most guidelines recommend not eating below 1,200 kcal/day for women or 1,500 kcal/day for men without medical supervision. If your TDEE minus your target deficit puts you below these levels, reduce the deficit — not the floor.
Step 3 — Set your daily calorie target
Your daily calorie target = TDEE − deficit.
TDEE: 1,849 kcal/day
Chosen deficit: 500 kcal/day (moderate)
Daily target: 1,349 kcal/day
Expected loss: ~1 lb/week · 10 lbs in ~10 weeks
This is the number to hit consistently — not a minimum or a maximum, but a target. Eating slightly over on some days and under on others is normal and doesn't undermine progress as long as the weekly average is close to the target.
Why protein intake matters in a deficit
When you eat fewer calories than you burn, your body draws on stored energy — ideally fat. But if protein intake is too low, the body also breaks down muscle tissue for energy. This is called muscle catabolism, and it's the primary reason people can lose significant weight but end up looking "skinny fat" rather than lean.
Research consistently shows that eating 1.6–2.4 g of protein per kg of bodyweight during a calorie deficit preserves lean muscle mass far better than eating at the RDA (0.8 g/kg). For someone at 65 kg, that's 104–156 grams of protein per day.
High protein intake also increases satiety — gram for gram, protein reduces hunger more than carbs or fat, making a deficit easier to stick to. Use our protein calculator to find your target alongside your calorie goal.
Why the deficit needs to adjust over time
TDEE isn't fixed. As you lose weight, your BMR decreases — a smaller body burns fewer calories at rest. This is why weight loss typically slows after the first few weeks even if nothing else changes.
Every 10 lbs of weight lost reduces TDEE by roughly 50–100 calories per day. Plan to recalculate your TDEE and adjust your calorie target every 4–6 weeks, or whenever progress stalls for more than 2–3 weeks.
When to recalculate:
Common mistakes that stall fat loss
- Underestimating calories. Studies show people underestimate their food intake by 20–40% on average. Tracking accurately — at least for a few weeks — is the most useful calibration exercise.
- Overestimating exercise calories burned. Fitness trackers and cardio machines typically overstate burn by 20–30%. Don't "eat back" all exercise calories unless you're genuinely hungry.
- Deficit too large. Aggressive deficits increase cortisol, accelerate muscle loss, and almost always lead to rebound eating. Slower is almost always better for long-term outcomes.
- Neglecting protein. The single most protective thing you can do during fat loss is eat sufficient protein. Most people under-eat it.
- Not adjusting as weight drops. A deficit that produced 1 lb/week at 200 lbs will produce less loss at 180 lbs. Recalculate periodically.
Calculate your deficit in seconds
Enter your stats and our calorie deficit calculator computes your TDEE, recommends a deficit size, and shows a week-by-week weight loss projection.