Calorie Deficit Calculator: How Many Calories to Eat to Lose Weight
Use this free calorie deficit calculator to find exactly how many calories to eat per day to lose weight. Enter your stats and goal weight, choose your pace (or a deadline), and get your daily calorie target, the size of your deficit, how long it will take, and your estimated goal date. Works in both imperial (lbs/ft) and metric (kg/cm).
Projected progress
Estimates only. Your metabolism adapts as you lose weight, so recalculate every 10 lbs (4-5 kg) and adjust based on your real weight trend.
What Is a Calorie Deficit?
A calorie deficit means eating fewer calories than your body burns. When you do this consistently, your body makes up the difference by using stored energy, mostly body fat. A calorie deficit is the one non-negotiable requirement for fat loss, no matter which diet you follow: low carb, keto, intermittent fasting, or simply eating less of what you already eat.
The size of the deficit matters. Too small and progress is painfully slow. Too large and you risk losing muscle, feeling exhausted, and quitting. This calculator helps you find the sweet spot for your body and your timeline.
How Does the Calorie Deficit Calculator Work?
The calculator follows four simple steps:
Step 1: Estimate your BMR using the Mifflin-St Jeor equation, widely considered the most accurate formula for most people.
Women: BMR = (10 x kg) + (6.25 x cm) - (5 x age) - 161
Step 2: Calculate your TDEE (maintenance calories) by multiplying your BMR by an activity factor from 1.2 to 1.9.
Step 3: Convert your goal to a daily deficit. One kilogram of body fat holds roughly 7,700 calories (about 3,500 calories per pound), so:
Step 4: Subtract the deficit from your TDEE to get the number of calories to eat each day.
How Big Should Your Calorie Deficit Be?
| Pace | Deficit | Best for |
|---|---|---|
| 0.5 lb (0.25 kg) per week | about 250 kcal/day | Lean people, slow and steady fat loss with maximum muscle retention |
| 1 lb (0.5 kg) per week | about 500 kcal/day | The best balance for most people |
| 1.5 lb (0.75 kg) per week | about 750 kcal/day | Higher body weight, short fat loss phases |
| 2 lb (1 kg) per week | about 1,000 kcal/day | Only for people with significant weight to lose, ideally with professional guidance |
A common guideline is to lose about 0.5% to 1% of your body weight per week. Going faster than that increases the risk of muscle loss, fatigue and rebound overeating.
Calorie Deficit Tips That Actually Work
- Eat enough protein. Aim for about 0.7-1 gram per pound of body weight (1.6-2.2 g/kg) to protect muscle while you lose fat.
- Lift weights. Resistance training tells your body to keep muscle while burning fat.
- Walk more. Daily steps raise your NEAT (non-exercise activity) and make the deficit easier to reach without eating less.
- Prioritize high-volume, low-calorie foods such as vegetables, fruit, potatoes, lean meats and soups to stay full.
- Track your weight weekly, not daily. Water, salt and hormones move the scale by several pounds. Use a 7-day average.
- Sleep 7-9 hours. Poor sleep increases hunger and cravings, making a deficit harder to maintain.
- Take diet breaks. After 8-12 weeks, spend 1-2 weeks at maintenance calories to recover mentally and physically.
Why You May Not Be Losing Weight in a Deficit
If the scale is stuck for 2-3 weeks, check these common causes:
- Underestimating intake. Oils, sauces, drinks and weekend meals add up quickly. Weigh your food for a week to check.
- Overestimating activity. Pick the lower activity level when in doubt.
- Water retention. A new workout routine, high sodium or stress can mask fat loss for days or weeks.
- Metabolic adaptation. As you get lighter, your TDEE drops. Recalculate after every 10 lbs (4-5 kg) lost.
- Inconsistency. Five perfect days and two big days can erase the whole weekly deficit.
Is a Very Low Calorie Diet Safe?
As a general guideline, adults should not eat below about 1,200 calories per day (women) or 1,500 calories per day (men) without medical supervision. Very low calorie diets can cause nutrient deficiencies, muscle loss, gallstones, hair loss and low energy. If your result lands below these numbers, choose a slower pace or a longer timeline instead.
Frequently Asked Questions About Calorie Deficits
How many calories should I cut to lose 1 pound a week?
You need a deficit of about 500 calories per day, or 3,500 calories per week, to lose roughly 1 lb (0.45 kg) of fat per week. You can create it by eating less, moving more, or a mix of both.
How do I calculate my calorie deficit?
First find your maintenance calories (TDEE). Then subtract your desired deficit. For example, if your TDEE is 2,400 and you want to lose about 1 lb per week, eat around 1,900 calories per day.
Is a 500 calorie deficit enough?
Yes. A 500 calorie deficit is the most popular and sustainable choice for most people. It leads to about 1 lb (0.5 kg) of fat loss per week while leaving enough energy for workouts.
How long does it take to lose 10 pounds?
At a pace of 1 lb per week, losing 10 lbs takes about 10 weeks. At 0.5 lb per week it takes around 20 weeks. Use the calculator above to get your personal timeline and goal date.
Is the 3,500 calorie rule accurate?
It is a useful approximation, but not exact. As you lose weight, your metabolism slows, so real-world loss is often slightly slower than the simple math predicts. That is why this calculator recommends recalculating regularly.
Should I create a deficit with diet or exercise?
Both work, but diet changes are usually easier to control. The best plan combines a moderate food deficit with strength training and daily walking.
Can I lose fat and build muscle at the same time?
Yes, especially if you are a beginner, returning after a break, or carrying more body fat. Use a small deficit, high protein and progressive strength training.
Disclaimer: This calculator is for educational purposes only and is not medical advice. Consult a doctor or registered dietitian before starting a weight loss plan, especially if you are pregnant, under 18, or have a medical condition.
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