Working backward from a weight-loss goal to the daily calorie deficit needed to reach it.
How it works
The target weight loss in pounds is multiplied by the widely used 3,500-kcal-per-pound approximation, then divided by the number of days to find the required daily deficit.
What this does not include
This does not include your total daily calorie needs — for that starting figure, use this site’s daily calorie needs calculator instead. This tool calculates only the deficit needed on top of that baseline.
How to use this calculator
- Enter your target weight loss and the timeframe.
A worked example
Target: lose 10 lb over 70 days → total deficit needed = 10 × 3,500 = 35,000 kcal, spread over 70 days = 500 kcal/day.
Target: lose 5 lb over 30 days → 5 × 3,500 ÷ 30 = 583.33 kcal/day — a noticeably steeper daily deficit for a faster timeline.
What the variables mean
| Variable | Meaning |
|---|---|
| Target weight loss | Goal amount, in pounds |
| Timeframe | Days to reach that goal |
| 3,500 kcal/lb | The long-standing approximation for energy stored per pound of body fat |
Edge cases worth knowing
3,500 kcal/lb is an approximation, not an exact conversion. More recent research shows the real relationship between calorie deficit and weight loss isn’t perfectly linear, especially over longer periods, as the body adapts.
A larger daily deficit isn’t automatically the better choice. Very large deficits can be difficult to sustain and may not be appropriate without guidance from a healthcare provider — this calculator reports the number, not whether it’s a wise target.
Frequently asked questions
Is 3,500 calories per pound an exact figure?
It’s a long-standing approximation, not a precise guarantee — more recent research shows the real relationship between calorie deficit and weight loss isn’t perfectly linear, especially over longer periods.
Is a larger daily deficit always better for faster results?
Not necessarily safe or sustainable — very large deficits can be difficult to maintain and may not be appropriate without guidance from a healthcare provider.
Does this account for changes in metabolism during weight loss?
No — this is a simplified linear estimate; actual metabolic adaptation during sustained weight loss can shift the real deficit needed over time.
