Intermittent fasting weight loss calculator
Pick a fasting schedule and see how much weight you might lose. You get your eating window, daily deficit and a 12-week projection.
Intermittent fasting calculator examples
Sample people, made up to show how the numbers change. Load one into the calculator to tweak it.
Lin, 16:8
Lin, 52, 162 cm (5'4"), 92 kg (203 lb), desk job, 16:8 starting at noon, 1,500 calories
In 12 weeks
196 lb
from 203 lb today
- Maintenance
- 1,820 cal
- Eating-day calories
- 1,500 cal
- Daily deficit
- 320 cal
- Eating window
- 12 pm to 8 pm
| Week | Weight |
|---|---|
| Week 4 | 200 lb |
| Week 8 | 198 lb |
| Week 12 | 196 lb |
| Week 26 | 188 lb |
- Fasting works by making a calorie deficit easier to keep. The window itself does not burn extra fat.
Dev, 5:2
Dev, 34, 178 cm (5'10"), 84 kg (185 lb), works out 3-5 days a week, 5:2 eating maintenance on normal days
In 12 weeks
170 lb
from 185 lb today
- Maintenance
- 2,770 cal
- Average a day (incl. 2 fast days)
- 2,100 cal
- Daily deficit
- 670 cal
- Fast days
- 2 non-consecutive days at about 600 cal
| Week | Weight |
|---|---|
| Week 4 | 180 lb |
| Week 8 | 175 lb |
| Week 12 | 170 lb |
| Week 26 | 156 lb |
- Fasting works by making a calorie deficit easier to keep. The window itself does not burn extra fat.
How the intermittent fasting calculator works
Intermittent fasting helps by making a calorie deficit easier to keep. In a year-long trial, people who ate within an 8-hour window lost about the same as people who cut the same calories without a window.
We work out your maintenance (Mifflin-St Jeor), compare it with what you plan to eat, and project your weight week by week, recalculating maintenance as you go.
For 5:2, fast days are 500 calories for women and 600 for men, with normal eating on the other five days.
Frequently asked questions
How much weight can I lose with intermittent fasting?
It depends on your deficit, not the window. A 500-calorie daily deficit is roughly 0.5 kg (1 lb) a week at first.
Is 16:8 or 5:2 better for weight loss?
They work about the same when calories match. Pick the one that fits your life.
Can I eat fast food while fasting?
Yes, in your eating window. Pleit helps you pick meals that fit your calories.
Sources
- Liu et al. (2022), calorie restriction with or without time-restricted eating, NEJM
- Mifflin et al. (1990), a new predictive equation for resting energy expenditure
- Hall (2008), what is the required energy deficit per unit weight loss?
These tools give estimates for healthy adults. They are not medical advice. If you are pregnant, under 18 or managing a health condition, check with your doctor or a registered dietitian.