Calorie Deficit Calculator
Find your maintenance calories, pick a deficit, and see how many weeks it will really take to reach your goal weight.
Fill in your details above to see your daily calorie target and how long it will take to reach your goal
What is a calorie deficit?
A calorie deficit means eating fewer calories than your body burns in a day. Your body makes up the difference from stored energy, mostly body fat, and over weeks that shows up as weight loss. Every diet that works, whether it is keto, intermittent fasting or plain portion control, works by creating a deficit. The calculator above tells you how big yours needs to be and what it means in calories on your plate.
How the calculator works
It runs in three steps, the same way a dietitian would do it by hand.
- Resting burn (BMR). Your basal metabolic rate comes from the Mifflin-St Jeor equation: 10 × weight in kg + 6.25 × height in cm − 5 × age, then +5 for men or −161 for women.
- Daily burn (TDEE). BMR is multiplied by an activity factor, from 1.2 for a desk job with no exercise to 1.9 for athletes and physical jobs. This is your maintenance level.
- Your target. The deficit you choose is subtracted from maintenance. The calculator never goes below 1,200 calories for women or 1,500 for men, the usual floors for dieting without medical supervision.
How big should your deficit be?
| Daily deficit | Expected loss | Best for |
|---|---|---|
| 250 calories | About 0.5 lb (0.2 kg) a week | The last 10 lb, or anyone who hates feeling hungry |
| 500 calories | About 1 lb (0.45 kg) a week | Most people. The standard starting point |
| 750 calories | About 1.5 lb (0.7 kg) a week | People with more to lose and a higher TDEE |
| 1,000 calories | About 2 lb (0.9 kg) a week | Short phases only, and only with a large starting weight |
A good rule is to aim for losing 0.5% to 1% of your body weight per week. Faster than that and you lose more muscle, feel worse, and are more likely to rebound.
Why your timeline is longer than the 3,500 calorie rule says
The classic rule says a pound of fat holds about 3,500 calories, so a 500 calorie daily deficit loses a pound a week forever. It doesn't quite work that way. As you get lighter, your body burns less, so the same intake becomes a smaller deficit and weight loss slows down.
The calculator accounts for this. It simulates your weight week by week and recalculates your maintenance as you go. For example, a 35 year old woman who is 5'5", 180 lb and lightly active burns about 2,080 calories a day. Eating 1,580 to reach 150 lb takes about 38 weeks, not the 30 weeks the simple rule predicts. Knowing that up front stops the "why has it slowed down?" panic in month five.
Making the deficit actually happen
The number is the easy part. Hitting it every day is where most people struggle, because nearly everyone underestimates how much they eat, often by hundreds of calories. Cooking oil, drinks, sauces and weekend meals are the usual culprits. Tracking what you eat, even roughly, is the most reliable way to close that gap. If logging feels like a chore, Bento Bunny lets you snap a photo or type a sentence like "chicken burrito bowl with guac" and fills in the calories for you.
Not sure what your maintenance is in the first place? Try the daily calorie calculator, or work out your macros once you have a target.
Frequently Asked Questions
How do I calculate my calorie deficit?
Is a 500 calorie deficit enough to lose weight?
Is a 1,000 calorie deficit safe?
Why have I stopped losing weight on the same calories?
Should I eat back the calories I burn exercising?
How long will it take to reach my goal weight?
What is the minimum number of calories I should eat?
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