On 16:8 you eat within an 8-hour window and then take a 16-hour break. If your last meal is at 8pm, your fast ends at 12pm the next day and your eating window is 12pm to 8pm. The calculator works this out for your own times, for 18:6, 14:10 and 12:12 too.
On 16:8 you eat within an 8-hour window and then take a 16-hour break. If your last meal is at 8pm, your fast ends at 12pm the next day and your eating window is 12pm to 8pm. The calculator works this out for your own times, for 18:6, 14:10 and 12:12 too.
Example:
12pm–8pm
Last meal at 8pm: your fast ends at 12pm the next day.
Not under 18, in pregnancy or while breastfeeding, with an eating disorder (now or in the past) or if you are underweight. On medication, check with your doctor first.
16 hours is plenty: more hours aren’t better.
During the break: water and drinks without calories, such as unsweetened tea or black coffee.
The calculator asks for:
The calculation runs in your browser. Your details are not saved and not sent anywhere.
Eating window if your last meal is at 7pm or 8pm. The app has 16:8 and 18:6.
| Schedule | Break | Eating | Last meal 7pm | Last meal 8pm |
|---|---|---|---|---|
| 12:12 | 12 h | 12 h | 7am–7pm | 8am–8pm |
| 14:10 | 14 h | 10 h | 9am–7pm | 10am–8pm |
| 16:8 | 16 h | 8 h | 11am–7pm | 12pm–8pm |
| 18:6 | 18 h | 6 h | 1pm–7pm | 2pm–8pm |
On the left worked out from your last meal, on the right from your first.
| Last meal | Fast ends | Eating window |
|---|---|---|
| 6pm | 10am (next day) | 10am–6pm |
| 7pm | 11am (next day) | 11am–7pm |
| 8pm | 12pm (next day) | 12pm–8pm |
| 9pm | 1pm (next day) | 1pm–9pm |
| 10pm | 2pm (next day) | 2pm–10pm |
| First meal | Eat until | Fast until |
|---|---|---|
| 8am | 4pm | 8am (next day) |
| 10am | 6pm | 10am (next day) |
| 11am | 7pm | 11am (next day) |
| 12pm | 8pm | 12pm (next day) |
| 1pm | 9pm | 1pm (next day) |
Example: Schedule 16:8, last meal at 8pm:
16 hours after your last meal. If your last meal is at 8pm, you can eat again from 12pm the next day, until 8pm.
Yes. The break starts with your last meal, and the night is part of it. That’s why on 16:8 a large part of the break happens while you sleep.
Start small: a 12-hour break first (12:12), then one hour more each week. Whether you stay at 14 or 16 hours is up to you. More hours aren’t better.
Water, unsweetened tea and black coffee. Milk in your coffee, juice, fizzy drinks, smoothies and alcohol all have calories and end the break.
As much as you’d normally eat in a day, just in fewer hours. Fasting doesn’t mean eating less than you need. Eating under 1,200 kcal a day (women) or 1,500 kcal (men) over a longer period isn’t a good idea.
Anyone pregnant or breastfeeding, anyone with an eating disorder (now or in the past), anyone underweight and anyone under 18. With diabetes or medication, only after talking to your doctor.
No. The calculator works in your browser and sends nothing.