Calorie Deficit Calculator

What This Tool Does

This calorie deficit calculator estimates the daily calorie deficit needed to reach a target weight by a target date, based on your sex, age, height, current weight, and activity level.

You can also use this GATE Calculator

How It’s Calculated

Step 1 — Basal Metabolic Rate (BMR), using the Mifflin-St Jeor equation:

• Men: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age(years) + 5
• Women: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age(years) − 161

Step 2 — Total Daily Energy Expenditure (TDEE) = BMR × Activity Multiplier (roughly 1.2 for sedentary, up to around 1.725–1.9 for very active).

Step 3 — Calorie Deficit = TDEE − Daily Calorie Intake

As a rough guide, 3,500 kcal of deficit is commonly associated with about 1 pound (0.45 kg) of fat loss — though this is a simplified approximation, not a precise individual prediction.

Worked example: Woman, 32 years old, 165 cm, 70 kg, moderately active.

• BMR: (10 × 70) + (6.25 × 165) − (5 × 32) − 161 = 700 + 1,031.25 − 160 − 161 = 1,410 kcal/day
• TDEE: 1,410 × 1.55 (moderately active) ≈ 2,186 kcal/day
• Targeting a moderate 0.5 kg/week loss (~550 kcal/day deficit): recommended intake ≈ 2,186 − 550 = ~1,636 kcal/day

Edge Cases and Special Rules

• There’s a general safe minimum intake: Commonly cited floors are around 1,200 kcal/day for women and 1,500 kcal/day for men — a calculated deficit shouldn’t push intake below this without medical supervision.
• TDEE changes as weight changes: A fixed deficit target needs periodic recalculation as your weight shifts, since a lighter body typically burns somewhat fewer calories at the same activity level.
• Larger isn’t better: Deficits much beyond 500–750 kcal/day generally aren’t recommended — they increase the risk of muscle loss, fatigue, and are harder to sustain, without necessarily speeding up meaningful long-term results.
• Individual response varies: Metabolic response to a calorie deficit differs meaningfully from person to person, so results are reasonable estimates, not guarantees.

BMR → TDEE → Calorie Deficit

These three concepts build on each other in order. BMR is the energy your body needs at complete rest, just to maintain basic functions. TDEE adds your activity level on top of BMR, giving your true total daily energy need. Calorie deficit is what happens when your actual intake falls below TDEE — the gap between the two is what drives weight loss over time. Understanding this chain makes it clear why activity level changes your calorie needs even if your BMR stays the same.

Who Uses This

• People planning a gradual, healthy weight-loss approach
• Anyone wanting to understand the math behind a diet plan before starting one
• People combining calorie tracking with exercise for weight management
• Those checking whether a specific diet plan’s calorie target falls within a healthy range

Calorie Deficit vs. Calorie Surplus

These sit on opposite sides of the same equation. A calorie deficit — eating below TDEE — drives weight loss over time. A calorie surplus — eating above TDEE — supports weight and muscle gain, since it provides extra energy for building tissue. Muscle building generally requires a surplus, though a mild deficit combined with adequate protein and resistance training can, for some people, support modest muscle retention or gain (often called body recomposition) — a more nuanced case than the simple deficit/surplus split.

FAQ

What is a calorie deficit?

Consuming fewer calories than your body burns (TDEE), which over time results in weight loss.

How many calories should I cut to lose weight safely?

A deficit of around 500 kcal/day is commonly recommended for a moderate, sustainable pace of about 0.5 kg (1 lb) per week.

Is it safe to eat very few calories to speed up weight loss?

No — dropping below roughly 1,200 kcal/day (women) or 1,500 kcal/day (men) without medical supervision isn’t recommended and can be harmful.

Can I build muscle while in a calorie deficit?

It’s possible in some cases, particularly with adequate protein intake and resistance training, though a surplus is generally more effective for muscle building specifically.

How long will it take to see results?

It varies by individual, but a 500 kcal/day deficit is commonly associated with roughly 0.5 kg of weight loss per week.

Try It Above

Enter your details and target weight in the calorie deficit calculator above to get a personalized estimate. This is general educational information, not medical advice — consult a doctor or registered dietitian before starting any significant calorie-restricted diet.