What is a calorie deficit?

A calorie deficit happens when you consistently eat fewer calories than your body burns. Your body still needs energy every day (to keep your heart beating, power your brain, and move your muscles), so when food energy is lower than energy use, your body makes up the difference by using stored energy — mostly from body fat, and sometimes from muscle if the deficit is too aggressive.

Think of it like a bank account. Your maintenance calories (also called TDEE: Total Daily Energy Expenditure) are your “break-even” number. If you eat about that amount, your weight tends to stay stable over time. If you eat above maintenance, you’re in a surplus (weight gain trend). If you eat below maintenance, you’re in a deficit (weight loss trend).

This calculator estimates your maintenance calories and then converts your chosen goal (for example, losing 0.5 kg per week or 1 lb per week) into a daily calorie target. It also shows a “smart safety” range so you don’t accidentally set your calories too low.

• Small deficit (5–10%): easier to sustain, slower loss, great for recomposition.
• Moderate deficit (10–20%): common “cutting” range, solid results without misery.
• Aggressive deficit (20–30%+): faster loss but higher hunger, fatigue, and muscle-loss risk.

Step-by-step method (simple but accurate)

Behind the scenes, we estimate your energy needs in two layers:

BMR is the calories your body would burn if you did nothing but breathe all day. We use the popular Mifflin–St Jeor equation because it performs well for most adults. It uses your sex, age, height, and weight.

TDEE is BMR multiplied by an activity factor. If you sit most of the day, your factor is lower. If you train frequently and move a lot, it’s higher. We also show your activity factor so you can sanity-check it.

Fat loss happens when energy intake stays below energy use long enough. A widely used estimate is:

• ~7,700 kcal ≈ 1 kg of body fat (approximation).
• ~3,500 kcal ≈ 1 lb of body fat (approximation).

So if your goal is 0.5 kg/week, that’s roughly 3,850 kcal/week — about 550 kcal/day. Your daily target becomes: Target calories = TDEE − daily deficit.

Real life isn’t perfectly linear: water weight shifts, sodium changes, muscle glycogen, hormones, sleep, and stress all affect the scale. That’s why we also show a realistic range and suggest using weekly averages instead of reacting to a single weigh-in.

How to use your calorie deficit number (without burning out)

Once you have your daily target, the easiest way to succeed is to treat it like a budget: you don’t need perfection every day — you need consistency across the week. Many people do best aiming for a weekly calorie goal (daily target × 7) and then letting life happen.

• Protein first: higher protein supports fullness and helps preserve muscle while dieting.
• Fiber helps: fruits, vegetables, beans, and whole grains make dieting easier.
• Steps matter: non-exercise movement (NEAT) can change TDEE a lot.
• Strength train: signals your body to keep muscle during weight loss.
• Sleep: poor sleep increases hunger and makes adherence harder.
• Plan the “hard moments”: weekends, travel, social meals — decide your strategy ahead of time.

• ½ plate: veggies / fruit
• ¼ plate: lean protein
• ¼ plate: carbs or fats (choose the one you enjoy most)

Many people cut calories, but unconsciously reduce movement (fewer steps, more sitting). That drops TDEE and can stall progress. If fat loss slows, increasing daily steps is often the simplest fix.

Calorie deficit examples (with real numbers)

Maintenance (TDEE): 2,400 kcal/day
Goal: 0.5 kg/week (~550 kcal/day deficit)
Target intake: ~1,850 kcal/day
Note: If this feels too hard, try 0.25 kg/week (smaller deficit).

Maintenance (TDEE): 2,000 kcal/day
Goal: 10% deficit (~200 kcal/day)
Target intake: ~1,800 kcal/day
Why it works: easier adherence → more months of progress.

Maintenance (TDEE): 3,000 kcal/day
Goal: 1.0 kg/week (~1,100 kcal/day deficit)
Target intake: ~1,900 kcal/day
Warning: This is tough. Prioritize protein + strength training, and consider diet breaks.

Daily target: 1,900 kcal → weekly budget = 13,300 kcal.
If you have a social dinner and eat 2,400 kcal one day, you can simply eat 1,800 kcal the next day to balance the week. This is often easier than trying to be perfect every day.

Frequently Asked Questions

• Is a calorie deficit the only way to lose fat?

  For fat loss, yes — the body must use stored energy, which requires a deficit over time. Different diets (keto, intermittent fasting, low-fat, Mediterranean) can work, but they work because they help you maintain a calorie deficit more easily.

• What deficit is “safe”?

  Many adults do well with a 10–20% deficit or about 250–750 kcal/day depending on size and activity. If your target calories drop extremely low, choose a slower loss rate or consult a clinician.

• Why is my scale not moving even in a deficit?

  Common reasons: water retention (salt, stress, soreness), inconsistent tracking, weekend “calorie creep,” or your estimated TDEE is higher than your true maintenance. Use weekly averages and adjust by 100–200 kcal/day.

• Do I need to count calories?

  Not always. Some people succeed using portion control, meal templates, and high-protein habits. Calorie counting is a tool — helpful if you’re stuck, but not required forever.

• Should I eat back exercise calories?

  Usually, only partially (or not at all) unless you’re doing high-volume endurance training. Fitness trackers often overestimate burn. A safer strategy is to keep a consistent target and adjust based on results.

• What if I’m losing weight too fast?

  Increase calories by ~100–200 per day, reduce cardio slightly, and prioritize protein and strength training. Fast loss can be motivating, but overly aggressive dieting can increase fatigue and muscle loss risk.

• How often should I update my deficit?

  Recalculate when your weight changes meaningfully (e.g., every 5–10 lb / 2–5 kg), when activity changes, or if progress stalls for 2–3 weeks.

Healthy boundaries (read this)

This calculator is built for general fitness planning. It is not medical advice. If you have a history of disordered eating, are pregnant, under 18, or have a medical condition, work with a qualified professional.

• Extremely low calorie targets can be unsafe and hard to sustain.
• Prioritize protein, strength training, and recovery during fat loss.
• Use weekly averages and trends, not single-day scale changes.
• Diet breaks can help adherence on longer cuts.

Pro tip: if you feel constantly exhausted, moody, or obsessed with food, your deficit is probably too large. Shrink the deficit and aim for sustainability.