Calorie Deficit to Weight Loss Timeline
Estimate how long it takes to lose a target amount of weight from a given daily calorie deficit, using the 3,500-calories-per-pound rule.
Result
- Total deficit required70,000 kcal
- Days to goal140
- Weeks to goal20.0
- Weekly loss rate1.00 lb/week
- Pace checkWithin the recommended safe range
Step-by-step
- Energy to lose 20 lb = 20 × 3500 = 70,000 kcal.
- Days = total ÷ daily deficit = 70,000 ÷ 500 = 140 days (20.0 weeks).
- That is about 1.00 lb per week.
How to use this calculator
- Enter your daily calorie deficit (calories eaten below maintenance).
- Enter the amount of weight you want to lose and its unit.
- Read the estimated weeks and days to reach your goal.
- Check the pace indicator to keep within a safe weekly rate.
About this calculator
Weight loss comes down to an energy deficit: eating fewer calories than your body burns. A long-standing rule of thumb, attributed to Max Wishnofsky, holds that a pound of body fat stores roughly 3,500 calories (about 7,700 calories per kilogram), so a sustained daily deficit predicts how fast you will lose. This calculator multiplies your target weight loss by that energy density to find the total deficit needed, then divides by your daily deficit to estimate the days and weeks to your goal. It also checks your implied weekly rate against the widely recommended safe range of one to two pounds (about half a kilogram to one kilogram) per week. Remember the rule is a simplification — real loss slows as your body adapts, and the figure is best treated as a planning estimate rather than a precise schedule.
How it works — the formula
Total deficit = Weight to lose × (3,500 kcal/lb or 7,700 kcal/kg)
Days = Total deficit ÷ Daily deficit
Weekly rate = Daily deficit × 7 ÷ kcal per unitThe energy stored in the target weight divided by the daily energy gap gives the time; the rule treats fat as a fixed energy store.
Worked examples
- Inputs:
- deficit=500, target=20, unit=lb
- Output:
- 70,000 kcal ÷ 500 = 140 days (20 weeks)
- Inputs:
- deficit=750, target=10, unit=kg
- Output:
- 77,000 ÷ 750 ≈ 103 days
- Inputs:
- deficit=1000, target=15, unit=lb
- Output:
- 52,500 ÷ 1,000 ≈ 52.5 days
Limitations
- Linear model; ignores metabolic adaptation that slows real loss.
- Does not distinguish fat, muscle, or water weight.
- Not individualized — true maintenance calories vary by person.
Educational estimate, not medical advice; consult a clinician for a weight-loss plan.