How to Calculate Calorie Deficit for Weight Loss (Step by Step)
A calorie deficit is the foundation of fat loss. No diet method, training protocol, or supplement overrides the basic principle: if your body consistently burns more calories than you consume, you lose body fat. But calculating the right deficit — one that drives results without burning through muscle or tanking your energy — requires more than just eating less.
This guide walks through the calculation step by step: finding your maintenance calories, setting a deficit that fits your goal, and adjusting when progress stalls. The math is straightforward. The execution is where most people struggle.
Step 1: Calculate Your TDEE (Maintenance Calories)
Your TDEE — Total Daily Energy Expenditure — is the number of calories you burn on an average day including all activity. This is your maintenance level. Any intake below this number creates a deficit. Any intake above it creates a surplus.
TDEE is calculated by first finding your Basal Metabolic Rate (BMR) using the Mifflin-St Jeor formula, then multiplying by an activity factor based on how much you move:
TDEE Calculation
Step 1: BMR (Men) = (10 × kg) + (6.25 × cm) − (5 × age) + 5 Step 1: BMR (Women) = (10 × kg) + (6.25 × cm) − (5 × age) − 161 Step 2: TDEE = BMR × Activity Factor (1.2 to 1.9)Activity factors: 1.2 sedentary, 1.375 lightly active, 1.55 moderately active, 1.725 very active, 1.9 extra active.
Example: A 30-year-old woman, 163 cm, 70 kg, moderately active (exercises 3–4 days/week). Her BMR is approximately 1,483 calories. Multiplied by 1.55, her TDEE is ~2,299 calories — the point at which her weight stays stable.
Step 2: Choose Your Deficit Size
The standard recommendation is a deficit of 300–500 calories per day. A 500-calorie daily deficit produces roughly one pound of fat loss per week — based on the established figure of approximately 3,500 calories per pound of body fat. A 300-calorie deficit produces a more moderate half-pound per week.
| Daily Deficit | Weekly Loss (estimated) | Best For |
|---|---|---|
| ~200 calories | ~0.4 lb / 0.18 kg | Athletes, body recomposition |
| ~300 calories | ~0.6 lb / 0.27 kg | Sustainable fat loss, muscle preservation |
| ~500 calories | ~1 lb / 0.45 kg | Standard weight loss target |
| ~750 calories | ~1.5 lb / 0.68 kg | Aggressive cut (short-term only) |
| 1,000+ calories | ~2 lb / 0.9 kg | Not recommended — high risk of muscle loss |
Using the example above: TDEE of 2,299 calories minus a 500-calorie deficit means a daily intake goal of ~1,799 calories. That is the target to eat toward. Not below BMR. Not a round number from an app. A specific, calculated figure based on her body and activity.
Step 3: Set Up Your Tracking System
A calorie deficit only works if you know what you are actually eating. Research consistently shows that people underestimate their food intake by 20–40%. This is not dishonesty — it is human perception. Small portions look bigger than they are, sauces and oils go untracked, and "healthy" foods like nuts and avocado are calorie-dense.
Track your calories using a food diary app for at least 2–3 weeks when starting out. Weigh food in grams rather than using cup measurements where possible — measuring cups are notoriously inconsistent for calorie-dense foods. After a few weeks of consistent tracking, most people develop an accurate intuitive sense of portion sizes and can ease off detailed logging.
Try Our Calorie Deficit Calculator
Calculate your daily calorie target for weight loss, muscle gain, or maintenance. See a 12-week weight projection based on your chosen rate of change.
Open CalculatorStep 4: Track Progress and Adjust
Your calculated deficit is a starting point, not a guarantee. After two full weeks at your target intake, compare actual weight change to expected loss. If you are losing significantly less than predicted, either your tracking has gaps or your actual TDEE is lower than the formula estimated. If you are losing more than expected, you may be losing water weight alongside fat — or your TDEE is higher than estimated.
Adjust your target based on real data, not frustration. If the scale has not moved in three consecutive weeks despite accurate tracking at your deficit, reduce your intake by 100–150 calories or increase activity. Do not make large adjustments — small, sustained changes outperform dramatic cuts every time.
Recalculate your TDEE every 5–10 pounds lost. As your body weight drops, your BMR decreases. A deficit calibrated for 200 lbs will no longer produce the same loss at 185 lbs. Staying current with your numbers prevents plateaus and keeps progress moving.
What to Avoid
Eating below your BMR is the most important line not to cross. Your BMR is the caloric floor for basic organ function. Long-term restriction below this level triggers adaptive thermogenesis — your metabolism slows, cortisol rises, muscle breaks down for fuel, and progress halts. Sustainable fat loss keeps intake above BMR while creating a deficit relative to TDEE.
Cutting calories too fast also backfires. A deficit larger than 1,000 calories per day tends to result in significant lean mass loss alongside fat, leaving you lighter but with a worse body composition and a lower TDEE going forward. Slow and steady genuinely does produce better body composition outcomes.
Not eating enough protein during a deficit accelerates muscle loss. Aim for at least 0.7–1 gram of protein per pound of body weight when in a calorie deficit. Protein also has the highest satiety per calorie of any macronutrient, making it easier to stay in your deficit without feeling deprived.