What is a calorie deficit?
A calorie deficit means your body uses more energy than you eat over time. When the gap is sustained, body weight usually trends downward because stored energy helps cover the difference.
How this calculator works
The calculator first estimates maintenance calories from your body data and activity level. If you provide a reasonable body-fat estimate, it can use Katch-McArdle; otherwise it uses Mifflin–St Jeor. It then applies the deficit plan you select and estimates a weekly rate and goal timeline.
What is a practical starting deficit?
Many adults begin around 10–20% below estimated maintenance. More aggressive targets may shorten the estimated timeline, but they can be harder to sustain and may increase fatigue, hunger and training difficulty.
Why the projection will not be exact
Real scale weight changes with water, glycogen, sodium, digestion, menstrual cycle, activity and tracking error. Use the result as a starting plan, then reassess after two to four weeks using average intake and weight trend.
Calorie Deficit FAQ
Should I always choose the fastest plan?
No. A plan only works when it can be followed consistently. A smaller deficit that you can sustain is often more useful than a larger one that repeatedly breaks down.
Should I eat below BMR?
Targets below estimated BMR can be too aggressive for many people, especially for long periods. The result page includes caution messages when the selected target crosses common guardrails.
Should I eat back exercise calories?
Be careful. If your activity multiplier already includes exercise, adding every tracker-reported exercise calorie back can erase the intended deficit.