Understanding This Calculator
Weight loss follows a straightforward energy-balance principle: one pound of body fat represents approximately 3,500 kilocalories of stored energy. A sustained daily calorie deficit, projected over time, therefore predicts a fairly linear rate of weight loss — though real-world results vary with water retention, metabolic adaptation, and adherence.
A moderate deficit of 500 kcal/day (roughly 1 lb/week) is the range most commonly recommended for sustainable, muscle-sparing fat loss; very large deficits accelerate short-term loss but increase muscle loss risk and are harder to sustain.
- 3,500 kcal estimated energy in one pound of body fat
- deficit daily calories below maintenance
| Daily Deficit | Weeks to Lose 10 lb |
|---|---|
| 250 kcal | 20.0 weeks |
| 500 kcal | 10.0 weeks |
| 750 kcal | 6.7 weeks |
| 1000 kcal | 5.0 weeks |
Frequently Asked Questions
Is the 3,500 kcal-per-pound rule still considered accurate?
It’s a useful approximation for planning, though research shows the real relationship isn’t perfectly linear — metabolic adaptation tends to slow loss somewhat as a deficit continues over many weeks.
What’s a safe deficit size?
Most guidelines recommend 500-750 kcal/day for sustainable loss of about 1-1.5 lb/week; larger deficits should generally be supervised by a healthcare provider.