Health & Fitness

Calorie Deficit

How long will it take to reach your goal weight at a given calorie deficit?

Weight loss is governed by energy balance. A sustained calorie deficit causes fat loss at a predictable rate. This calculator shows the timeline based on the widely-used 3,500 calories-per-pound rule.

Enter your numbers

Current Weight (lbs)

Target Weight (lbs)

Daily Calorie Deficit500cal

500/day = 1 lb/week. Avoid going below 1,200 cal total.

Results update as you change the inputs. Calculations run in your browser.

Time to Goal

25.0 Weeks

total Days: 175 days
lbs Per Week: 1.00 lbs/week
total Deficit: 87.5K cal to eliminate

See the formula

Formula and method

Days = (Lbs to Lose × 3500) / Daily Deficit

The 3,500 calorie = 1 pound rule is a widely-used approximation from metabolic research. In practice, the body adapts over time, so actual results vary. Best used for planning a starting point.

Worked examples

Gradual sustainable loss

Current Weight (lbs):: 200
Target Weight (lbs):: 175
Daily Calorie Deficit:: 400

Time to Goal: 31.3 Weeks

Aggressive cut

Current Weight (lbs):: 220
Target Weight (lbs):: 190
Daily Calorie Deficit:: 750

Time to Goal: 20.0 Weeks

Assumptions and limits

3,500 calories per pound rule
No metabolic adaptation
Deficit maintained consistently

This tool provides an educational estimate. Rules, rates and personal circumstances can change the answer. Review the assumptions before relying on a result. Report a correction.

Common mistakes to avoid

Creating too large a deficit — very low calorie diets cause muscle loss and metabolic adaptation.
Not accounting for metabolism slowdown as weight decreases — recalculate every 4-6 weeks.
Overestimating exercise calories burned — fitness trackers often overcount by 20-50%.

Frequently asked questions

Is 500 cal/day deficit safe?

Yes — a 500 cal/day deficit (1 lb/week loss) is generally considered the safe and sustainable upper limit for most people. Anything over 1,000 cal/day deficit should only be done under medical supervision.

Why is the actual result slower than predicted?

As you lose weight, your basal metabolic rate decreases (you burn fewer calories at rest). Additionally, the body adapts by reducing non-exercise activity. Recalculate your needs every 10-15 lbs of loss.