Popular fasting protocols
Intermittent fasting protocols are written as fasting hours : eating hours. The bigger the first number, the longer you fast and the tighter your eating window. Here is how the common methods compare:
| Protocol | Fast | Eat | Who it suits |
|---|---|---|---|
| 16:8 | 16 h | 8 h | The popular all-rounder; great first step |
| 18:6 | 18 h | 6 h | Once 16:8 feels easy and you want more |
| 20:4 | 20 h | 4 h | Experienced fasters comfortable with one or two meals |
| OMAD | 23 h | 1 h | One meal a day; advanced, needs careful nutrition |
How to choose a window
The best window is the one you can keep. Most people anchor the fast to sleep — stop eating after dinner, fast overnight, and break the fast late morning or at lunch. If you train in the morning or have an early family dinner, slide the window earlier. Start gentle with 14:10 or 16:8 and tighten only once it feels natural.
Fasting controls when you eat, not how much — it is not a licence to ignore calories. To pair a window with a calorie target, run the TDEE calculator first.
Fasting is easier with a partner
The hard part of fasting is the willpower, not the maths. That is why Swoodie includes a built-in fasting tracker with all of these protocols, plus Fast Together — a mode that lets you and your partner fast on a synced clock and nudge each other through the tough hours. Read how fasting with a partner works or see the full intermittent fasting guide.
Frequently asked questions
How does intermittent fasting work?
Intermittent fasting cycles between periods of eating and fasting. You eat all your food within a set window each day and consume only water, black coffee, or plain tea during the fast. The 16:8 method, for example, means 16 hours fasting and an 8-hour eating window.
What is the best intermittent fasting schedule for beginners?
Most beginners start with 14:10 or 16:8 because they are sustainable and largely overlap with sleep. You can stop eating after dinner, fast through the night, and break the fast late morning or at lunch. Tighter windows like 20:4 or OMAD are better once you have adapted.
When can I eat on 16:8?
With 16:8, your eating window is 8 hours long and opens 16 hours after you start fasting. If you stop eating at 8 PM, your fast ends and you can eat again at 12 PM the next day, with the window closing at 8 PM. Enter your own start time above to see your exact window.
Can I drink anything while fasting?
Yes. Water, black coffee, and plain tea are fine and do not break a fast. Avoid anything with calories — milk, sugar, juice, or sweetened drinks — as these can interrupt the fasted state.
Does this calculator use my current time?
No. It calculates your eating window purely from the start time you type in, so the result is stable and shareable. Change the start time to plan any schedule you like.
This tool is for general information and is not medical advice. Intermittent fasting is not suitable for everyone — including during pregnancy or breastfeeding, with a history of eating disorders, or while on certain medications. Speak to your doctor before starting.