How to Use This Calorie Deficit Calculator
Our free calorie deficit calculator gives you accurate estimates in seconds. Enter your numbers above and hit Calculate — results update instantly.
All calculations use current 2026 rates and formulas. Results are estimates to help you plan — always verify with a licensed professional for final numbers.
Frequently Asked Questions
What is a calorie deficit?
A calorie deficit means consuming fewer calories than your body burns. When you eat less than your TDEE, your body uses stored fat for energy, resulting in weight loss.
How big should my calorie deficit be?
A moderate deficit of 300-500 calories per day leads to 0.5-1 lb weight loss per week. A 500-1000 calorie deficit can lead to 1-2 lbs per week. Avoid deficits over 1000 calories as they can cause muscle loss.
How long to lose 10 pounds with a calorie deficit?
With a 500 calorie daily deficit, you lose about 1 pound per week. Losing 10 pounds would take approximately 10 weeks. With a 1000 calorie deficit, it could take 5 weeks.
Can I eat too little on a calorie deficit?
Yes. Eating too few calories (below 1200 for women, 1500 for men) can slow metabolism, cause muscle loss, nutrient deficiencies, and fatigue. A sustainable deficit is key for long-term success.
Do I need to exercise on a calorie deficit?
Exercise is not required but highly recommended. It increases your calorie burn, preserves muscle mass during weight loss, and improves overall health. Combining diet and exercise gives better results than diet alone.