Schedule, live timer and weekly plan
Intermittent Fasting CalculatorFind Your 16:8, 18:6 or OMAD Eating Window
Plan a fasting schedule that fits your day. Choose a plan such as 16:8, set when you want your first or last meal, and this intermittent fasting calculator shows your exact eating and fasting windows on a 24-hour clock. It also counts how many fasting hours fall while you sleep, runs a live fasting timer and builds a weekly plan.
- 7 fasting plans
- 24-hour clock view
- Live fasting timer
- Weekly planner
Adding your sleep hours shows how much of the fast happens while you sleep, which makes longer fasts easier to plan.
24-hour clock showing the eating window, fasting window and sleep
Nothing is saved on this site. To keep your timer, copy the resume link and open it later on any device.
Unselected days are regular eating days. Starting with fewer days and building up is a gentler approach.
What is intermittent fasting?
Intermittent fasting is an eating pattern that alternates between a fasting window and an eating window. It focuses on when you eat rather than what you eat. The most common approach is time-restricted eating, where you fast for a set number of hours each day and eat within the remaining hours.
For example, in the popular 16:8 plan you fast for 16 hours and eat within an 8-hour window, such as 12 pm to 8 pm. Because the overnight hours count toward the fast, much of it happens while you sleep.
| Plan | Fasting | Eating window | Example window | Often chosen by |
|---|---|---|---|---|
| 12:12 | 12 hours | 12 hours | 8 am to 8 pm | Complete beginners |
| 14:10 | 14 hours | 10 hours | 9 am to 7 pm | A gentle step up |
| 16:8 | 16 hours | 8 hours | 12 pm to 8 pm | Most people, the classic plan |
| 18:6 | 18 hours | 6 hours | 1 pm to 7 pm | Experienced fasters |
| 20:4 | 20 hours | 4 hours | 3 pm to 7 pm | Advanced, with medical advice |
| OMAD 23:1 | 23 hours | 1 hour | 6 pm to 7 pm | Advanced, with medical advice |
Is intermittent fasting right for you?
Fasting is not suitable for everyone. Talk to a doctor first if you are pregnant or breastfeeding, under 18, underweight, have diabetes or take medication that affects blood sugar, or have a history of disordered eating. Stop and seek advice if you feel unwell, dizzy or unusually tired.
A smarter fasting schedule calculator
Most fasting calculators give you two times and stop there. This one shows your whole day, keeps time for you and plans the week around real life.
24-hour clock
See eating, fasting and sleep on one clock, with a live marker for the current time.
Sleep overlap
Find out how many fasting hours happen while you sleep and how many you spend awake.
Live fasting timer
Track elapsed and remaining time with a progress ring, and resume it later with a private link.
Weekly planner
Set different meal times for weekdays and weekends and choose which days you fast.
Every popular plan
12:12, 14:10, 16:8, 18:6, 20:4 and OMAD, plus any custom number of hours.
Private and free
No account and no tracking. Everything runs in your browser, and nothing is stored.
How to use the intermittent fasting calculator
Pick a plan
Start with 12:12 or 14:10 if you are new, or choose 16:8 for the classic schedule.
Set a meal time
Enter your first meal or your last meal, whichever is easier to fix in your routine.
Add your sleep
Enter bedtime and wake-up to see how much of the fast you will sleep through.
Track and plan
Start the live timer for today, then build a weekly plan that fits work and weekends.
Planning what to eat in your window? Estimate your daily needs with the TDEE calculator and your protein target with the protein calculator.
Practical tips for intermittent fasting
Start gradually
Begin with a shorter fast and add an hour or two each week as your body adjusts.
Stay hydrated
Drink water through the fast. Use the water intake calculator to set a daily goal.
Eat balanced meals
Fill your window with protein, vegetables, whole grains and healthy fats rather than snacks.
Use your sleep
Place most of the fast overnight. A sensible bedtime makes the fast far easier to keep.
Be consistent, not perfect
A regular window most days matters more than a perfect streak. It is fine to adjust for events.
Listen to your body
Hunger usually eases with time, but dizziness or weakness is a sign to eat and seek advice.
Intermittent fasting FAQs
What is the 16:8 intermittent fasting schedule?
In 16:8 you fast for 16 hours and eat within an 8-hour window each day. A common example is eating between 12 pm and 8 pm, then fasting from 8 pm until 12 pm the next day.
How do I calculate my eating window?
Subtract your fasting hours from 24 to get the eating window length. Then add that length to your first meal time to find your last meal time. For 16:8 with a first meal at 11 am, the window closes at 7 pm.
Does sleep count as fasting?
Yes. The hours you sleep count toward your fast, which is why most people place the fasting window overnight. Enter your bedtime and wake-up time in the calculator to see the overlap.
What can I drink while fasting?
Water is always fine. Many people also drink plain black coffee or unsweetened tea. Drinks with sugar, milk or calories are generally counted as breaking the fast.
What is the best time for an eating window?
The best window is one you can keep consistently around work, family meals and sleep. Many people find an earlier window, such as 10 am to 6 pm, easier to align with an early bedtime.
Can I change my eating window on weekends?
Yes. Small shifts are common and usually fine. The Weekly plan tab lets you set a separate weekend first meal and choose which days you fast.
Is OMAD safe?
One meal a day is an advanced pattern that makes it harder to meet nutrient needs. It is not suitable for everyone, so speak with a doctor or dietitian before trying it.
Who should not try intermittent fasting?
People who are pregnant or breastfeeding, under 18, underweight, have a history of disordered eating, or have diabetes or take medication affecting blood sugar should get medical advice before fasting.
Build a fasting routine that fits your life
A clear schedule makes intermittent fasting far easier to stick with. Use this intermittent fasting calculator to plan your window, track today's fast and set up a realistic week.