Weight loss comes down to one simple idea: eat fewer calories than your body uses. That gap is your calorie deficit, and getting it right is the difference between steady, sustainable progress and a diet that leaves you hungry, tired, and ready to quit after two weeks. This guide shows you how to calculate your calorie deficit step by step, with real numbers you can copy for your own situation.
What Is a Calorie Deficit?
A calorie deficit happens when you consume less energy than your body expends. Your body makes up the shortfall by drawing on stored energy, mainly body fat. If you eat more than you burn, the surplus is stored instead. That is the whole mechanism — every successful weight-loss plan, whatever its name or rules, works because it creates a deficit, whether it does so by cutting portions, changing food choices, or adding activity.
Two numbers matter here. The first is your TDEE, or Total Daily Energy Expenditure: the total calories you burn in a day, including basic body functions, digestion, everyday movement, and exercise. The second is your daily calorie intake. The formula is simple:
Calorie deficit = TDEE − daily calories eaten
For example, if your TDEE is 2,400 calories and you eat 1,900 calories, your deficit is 500 calories per day. If you do not know your TDEE yet, use our free TDEE calculator first — it is hard to set a sensible target without it.
How to Calculate Your Calorie Deficit in 3 Steps
Step 1: Find your TDEE. This is your maintenance level — the calories that would keep your weight stable. Estimate it with a calculator, or by hand: work out your BMR (calories burned at rest) with the Mifflin-St Jeor equation, then multiply by an activity factor from 1.2 (sedentary) to 1.9 (very active).
Step 2: Choose your deficit. A deficit of 250 to 750 calories per day suits most people. A smaller deficit means slower but easier weight loss; a larger one means faster loss but more hunger and a higher risk of giving up. The table below shows what each level typically means in practice.
Step 3: Subtract. Your daily calorie target is your TDEE minus your chosen deficit. That target is the number to aim for on an average day — not a limit you must hit exactly at every single meal.
The 3,500-Calorie Rule — and What It Really Means
You have probably heard that one pound of body fat contains about 3,500 calories. The rule of thumb that follows is that a daily deficit of 500 calories adds up to 3,500 calories over a week, or roughly one pound (about 0.45 kg) of fat loss per week. In metric terms, one kilogram of body fat is roughly 7,700 calories, so a 500-calorie daily deficit points to about 0.45 kg per week.
Treat this as a guide, not a promise. Water retention, glycogen, hormones, and activity changes make the scale jump around day to day, and your TDEE falls slightly as you get lighter. Still, a 500-calorie deficit should produce visible progress over a month, even if any single week looks messy. Our free calorie calculator will work out your target from your age, weight, height, activity level, and goal.
Worked Examples With Real Numbers
Example 1 — Moderate deficit. Sara is 34, weighs 72 kg, and has a TDEE of 2,200 calories. She chooses a 500-calorie deficit: 2,200 − 500 = 1,700 calories per day. Over a week that is a 3,500-calorie deficit, pointing to roughly 0.45 kg of fat loss per week, or about 1.8 kg over a month if she stays consistent.
Example 2 — Gentle deficit. James is 45, weighs 88 kg, and has a TDEE of 2,800 calories. He prefers a gentler start, so he chooses a 300-calorie deficit: 2,800 − 300 = 2,500 calories per day. That points to about 0.27 kg per week — slower, but much easier to live with, and often the smarter choice for someone who has struggled with strict diets before.
Example 3 — Larger deficit. Priya is 29, weighs 95 kg, and has a TDEE of 2,600 calories. She chooses a 750-calorie deficit: 2,600 − 750 = 1,850 calories per day. That points to roughly 0.68 kg per week. Larger deficits can work, but they demand more attention to protein and food quality, because there is less room for error.
How Big Should Your Deficit Be?
| Deficit per day | Typical weekly loss | Best for |
|---|---|---|
| 250 calories | About 0.2 kg | Slow, low-hunger loss; people close to their goal weight |
| 500 calories | About 0.45 kg | The standard starting point for most people |
| 750 calories | About 0.7 kg | People with more to lose who can eat enough protein |
| 1,000 calories | About 0.9 kg | Short-term use only, and only if intake stays adequate |
As a general rule, aim to lose no more than about 0.5 to 1 percent of your body weight per week. For an 80 kg person, that is 0.4 to 0.8 kg per week. Faster than that, and a growing share of the loss tends to be muscle and water rather than fat — and hunger, fatigue, and cravings usually rise sharply.
There are also sensible floors. As general information only, many guidelines suggest adults avoid going below about 1,200 calories per day for women and 1,500 for men without professional guidance, as basic nutrition needs become hard to cover. If your target lands below a floor like that, choose a smaller deficit and add activity instead.
Should You Create the Deficit From Food, Exercise, or Both?
A mix of both usually works best. Cutting 500 calories from food is straightforward: skip the sugary drink, halve the takeaway portion, or swap a creamy sauce for a tomato-based one. Exercise alone is harder, because a 30-minute run might burn 300 calories — easily undone by one large snack — and exercise often increases appetite.
A practical split is to get most of your deficit from food and use exercise as a bonus. For instance, if your target deficit is 500 calories, aim to eat about 400 fewer calories and burn about 100 more through a daily walk. That way a missed workout does not wreck the week, and your eating does not have to be perfect either. Whatever you choose, keep protein up — roughly 1.6 to 2.2 grams per kilogram of body weight per day is a commonly cited range for people losing weight — because protein helps preserve muscle and keeps you fuller for longer.
Why Crash Diets Backfire
A 1,500-calorie deficit sounds tempting: lose weight three times as fast, right? In practice, very large deficits tend to backfire. Hunger hormones rise, energy drops, workouts suffer, and the diet becomes miserable to sustain. Many people then rebound, regain the weight, and end up heavier than when they started — not because the maths was wrong, but because the plan was unlivable.
There is also a quieter effect: when you eat far too little for weeks, your body adapts by burning slightly fewer calories, mainly through less spontaneous movement. That adaptation is modest, but it means extreme deficits deliver less than the simple maths suggests. A moderate deficit you can keep for three months beats an extreme one you abandon after ten days.
Common Mistakes When Calculating a Deficit
- Using someone else's number. A target that works for a friend may be far too high or low for you. Always start from your own TDEE.
- Forgetting liquid calories. Coffees with syrup, juice, alcohol, and smoothies can add 300 to 500 calories a day without feeling like food.
- Counting exercise twice. If your TDEE already includes your activity level, do not subtract workout calories again — that double-counts the same burn.
- Expecting a straight line. Weigh yourself a few times a week and compare weekly averages, not single days. Daily weight can swing by a kilogram or more from water alone.
- Never recalculating. As you lose weight, your TDEE drops. Recheck your target every 5 kg or so, or whenever progress stalls for three weeks.
Putting It All Together
Calculating a calorie deficit is a three-step job: find your TDEE, pick a deficit of 250 to 750 calories, and subtract. A 500-calorie daily deficit is a solid starting point for most people, pointing to roughly half a kilogram of fat loss per week. Build most of the deficit from food, support it with movement and enough protein, and avoid extremes that you cannot sustain.
This article is general information, not medical advice. If you have a medical condition, are pregnant, or have a history of disordered eating, talk to a healthcare professional before changing your diet. For everyone else, the best deficit is the one you can still be following in a month's time. Work out your number with our free calorie calculator, give it two or three consistent weeks, and adjust based on the trend, not a single weigh-in.
Frequently Asked Questions
What is a calorie deficit?
Eating fewer calories than your TDEE, so your body makes up the difference from stored energy.
How do I calculate my calorie deficit?
In three steps: find your TDEE, subtract your target deficit, and track your food intake against the resulting number.
How many calories are in a pound of fat?
Roughly 3,500 calories, so a 500-calorie daily deficit works out to about one pound per week, though real results vary.
How big should my calorie deficit be?
Moderate: around 300 to 500 calories a day. Aggressive deficits tend to backfire through hunger, muscle loss, and rebound eating.
Try it yourself: use our free Calorie Calculator to get your number in seconds — no sign-up needed.