Calorie Deficit Calculator

How much to eat to lose weight.

Use our free calorie deficit calculator to find how many calories you should eat per day to lose weight. Enter your sex, age, height, weight, activity level and desired deficit percentage — get your daily target in seconds.

A calorie deficit means eating fewer calories than your body burns (below your TDEE). It is what you need to lose weight. Our calorie deficit calculator works out your total daily energy expenditure (TDEE) using the Mifflin-St Jeor formula and your activity level, then applies the deficit percentage you choose (15%, 20%, or 25%) to give you a daily calorie target. This free calorie deficit calculator works for both women and men; for your TDEE only, use our TDEE calculator first.

What Is a Calorie Deficit?

A calorie deficit is when you eat fewer calories than your body burns in a day. Your body burns calories to maintain basic functions (breathing, circulation, digestion) and to fuel activity. That total burn is your TDEE (total daily energy expenditure). When you eat less than your TDEE, you are in a calorie deficit, and over time you lose weight. So when people search for “what is my calorie deficit” or “what should my calorie deficit be,” they usually want to know both the idea and a number: how many calories to eat per day. Our calorie deficit calculator gives you that number based on your TDEE and a chosen deficit percentage.

How to Calculate Calorie Deficit

You can calculate your calorie deficit online with the form above. Enter your sex, age, height, weight, activity level and the deficit percentage you want (15%, 20%, or 25%). The calculator first works out your TDEE (using BMR from the Mifflin-St Jeor equation × activity level), then applies the deficit. So you get: (1) your deficit in kcal per day, and (2) the calories you should eat per day to lose weight. If you already know your TDEE (for example from our TDEE calculator), you can work out a deficit yourself: multiply TDEE by (deficit % ÷ 100) and subtract that from TDEE.

Calorie deficit formula

The calorie deficit formula is: Deficit (kcal) = TDEE × (deficit % ÷ 100). Calories to eat = TDEE − Deficit. For example, if your TDEE is 2,000 kcal and you choose a 20% deficit, your deficit is 400 kcal and you should eat about 1,600 kcal per day. TDEE is calculated from your BMR (Mifflin-St Jeor) × activity factor. So “how to calculate calorie deficit” and “how to calculate a caloric deficit” both come down to knowing your TDEE and choosing a safe deficit percentage.

What Should My Calorie Deficit Be?

For most people, a deficit of 15–20% of TDEE is safe and sustainable. It is enough to lose weight without extreme hunger or fatigue. A 25% deficit is more aggressive and can speed up loss but may be harder to stick to and can increase the risk of losing muscle if protein and training are not adequate. So when you ask “what should my calorie deficit be” or “what calorie deficit should I be in,” a good answer is: start with 15% or 20%, and only consider 25% if you are comfortable with a faster pace and ideally have support (e.g. a dietitian). Our calculator offers 15%, 20% and 25% so you can compare; we show a short warning for 25% to remind you it is more aggressive.

Calorie Deficit for Weight Loss

To lose weight you need to be in a calorie deficit — eating below your TDEE. “How much of a calorie deficit to lose weight” depends on how fast you want to lose. A common guideline is about 500 kcal per day for roughly 1 lb (0.45 kg) of weight loss per week, but that is a fixed number; our calorie deficit calculator for weight loss uses a percentage of your TDEE, so the deficit scales with your size and activity. For example, 20% of a 2,500 kcal TDEE is 500 kcal; 20% of a 2,000 kcal TDEE is 400 kcal. So whether you search for “calorie deficit to lose weight calculator” or “calorie deficit calculator for weight loss,” the same tool applies: enter your data, choose 15%, 20% or 25%, and get your daily calories to eat.

Safe Calorie Deficit

A safe calorie deficit for most adults is in the 15–25% range of TDEE. Deficits much larger than 25% are not recommended without professional supervision: they can lead to muscle loss, fatigue and a higher chance of giving up. Our calculator only offers 15%, 20% and 25% for that reason. If you are unsure, start with 15% or 20%. Recalculate when your weight or activity changes.

When to Recalculate

Recalculate your calorie deficit when your weight has changed noticeably (for example by 5 kg or more), when your activity level changes, or every few months if you are tracking over time. As you lose weight, your TDEE tends to fall, so the same deficit percentage will give a lower “calories to eat” number — the calculator will show that when you run it again with your new weight.

Limitations and Disclaimer

This calorie deficit calculator is for screening and information only. It does not replace professional advice. It is not intended for children, or for pregnant or breastfeeding women, who have different energy needs. Always consult a doctor or dietitian for personalised nutrition and health advice.

Important: A 25% deficit is more aggressive. Consider 15–20% for most people. This tool does not replace medical or dietetic advice.

Related Calculators

Use our TDEE calculator to see your maintenance calories; our BMR calculator for resting calories; and our calorie calculator for tracking food. The BMI calculator can help you set a healthy target weight.

Frequently asked questions

A calorie deficit is eating fewer calories than your body burns (below your TDEE). It is required to lose weight. Our calorie deficit calculator uses your TDEE and a chosen deficit percentage to give you a daily calorie target.

Enter your sex, age, height, weight, activity level and desired deficit percentage in the form above. The calculator computes your TDEE, then your deficit in kcal and the calories you should eat per day.

Deficit (kcal) = TDEE × (deficit % ÷ 100). Calories to eat = TDEE − deficit. We compute TDEE from BMR (Mifflin-St Jeor) × activity level.

For most people, 15–20% of TDEE is safe and sustainable. 25% is more aggressive; avoid very large deficits without professional advice.

You need any deficit to lose weight; 300–500 kcal per day is often suggested for gradual loss. Our calculator uses percentage of TDEE (15%, 20%, 25%) so the deficit scales with your needs.

25% can be effective but is more aggressive; it may increase hunger and risk of muscle loss. We show a warning for 25%; 15–20% is safer for most.

Recalculate when your weight or activity changes noticeably, or every few months.

The calculator computes TDEE for you from your inputs. If you already know your TDEE, you can work out deficit yourself: multiply TDEE by (deficit % / 100) and subtract from TDEE.

Yes. Use our TDEE calculator to see your maintenance calories, then this calorie deficit calculator to get a daily target for weight loss.

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Content quality

Written by DietaBest Editorial Team

Medically reviewed by Dr. Alex Novak, MD (Internal Medicine)

Last updated:

This guide is for general education only and does not replace personal medical advice. Always talk to your doctor or a registered dietitian before making major diet or lifestyle changes, especially if you have a medical condition or take medication.