Calorie Deficit Calculator
Calculate how long it will take to reach your goal weight based on your daily calorie deficit.
About this tool
Our calorie deficit calculator uses the rule that 3,500 kcal equals approximately 1 lb of body fat. Enter your current weight, goal weight, and daily deficit to see your projected weekly weight loss and timeline to reach your goal.
How to use it
Quick steps to get the most out of this utility.
- 1
Enter your current weight
Select metric (kg) or imperial (lbs) and enter your current body weight.
- 2
Set your goal weight
Enter your target weight. The calculator will immediately show how far you need to go.
- 3
Choose your daily calorie deficit
Pick a deficit of 250, 500, 750, or 1000 kcal/day. Higher deficits mean faster results but require more discipline.
- 4
Review your projection
See your estimated weekly loss, time to goal, weight curve, and a comparison against other deficit levels.
How the calorie deficit calculator works
The calculator uses a well-established rule: 3,500 kcal of energy is approximately equal to 1 lb of body fat. If you maintain a daily deficit of 500 kcal, you will lose roughly 1 lb per week (500 × 7 = 3,500). The projections account for the fact that weight loss often slows over time as your body adapts, but use a linear model for simplicity.
The chart shows your projected weight at weeks 4, 8, 12, 16, 20, and beyond until you reach your goal. The comparison table lets you see how choosing a 250 kcal/day deficit versus 1,000 kcal/day affects your timeline — the difference is often striking.
Frequently asked questions
How does a calorie deficit work?+
A calorie deficit occurs when you consume fewer calories than your body burns each day. This forces your body to use stored fat for energy, leading to weight loss. A deficit of 3,500 kcal equals approximately 1 lb of body fat.
What is a safe calorie deficit for weight loss?+
A deficit of 250–750 kcal per day is generally considered sustainable and safe for most people. A 500 kcal/day deficit leads to about 1 lb of weight loss per week. Deficits above 1,000 kcal/day may cause muscle loss, nutrient deficiencies, and metabolic slowdown.
How long will it take to reach my goal weight?+
The time depends on your current weight, goal weight, and daily deficit. For example, a 500 kcal/day deficit with a 20 lb goal takes roughly 20 weeks. Use the calculator above to get a personalized projection.
Should I eat back the calories I burn from exercise?+
It depends on your goal. Eating back exercise calories can sometimes stall weight loss if estimates are inaccurate. If you prefer to eat back calories, use a conservative estimate and monitor your weight trend over 2–3 weeks before adjusting.
Is 1000 kcal deficit too aggressive?+
Yes, a 1,000 kcal/day deficit is generally considered aggressive and is not appropriate for most people. It may lead to muscle loss, fatigue, nutrient deficiencies, gallstones, and a slower metabolism. Consult a healthcare provider for personalized guidance.
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