Plan your fasting schedule. This free intermittent fasting calculator shows when your eating window opens and closes for 16:8, 18:6, 20:4 or OMAD — a timing planner, with no calorie or weight targets.
ℹ️ Intermittent fasting isn’t right for everyone. It’s generally not advised in pregnancy or breastfeeding, for those with a history of disordered eating, or for some people with diabetes or on certain medications. Check with a doctor first if any apply. This tool plans timing only — it doesn’t set calories or weight goals.
Your fasting plan
h fast
Enter when you finish your last meal. The calculator shows when your fasting window ends and your eating window opens and closes.
Eating window opens
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Choose a method and start time
Fasting window
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Eating window
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Fast / eat hours
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Window closes
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A timing guide for planning your eating window — it doesn’t recommend calories or weight goals. Stay hydrated during fasts, eat balanced meals in your window, and stop or seek advice if you feel unwell.
Use this free intermittent fasting calculator to plan your fasting and eating windows. Choose a method like 16:8, enter when you finish your last meal, and see exactly when your eating window opens and closes.
Note: intermittent fasting isn’t right for everyone. It’s generally not advised in pregnancy or breastfeeding, with a history of disordered eating, or for some people with diabetes or on certain medications. Check with a doctor first if any apply. This tool plans timing only — it doesn’t set calories or weight goals.
What this intermittent fasting calculator shows you
An intermittent fasting calculator works out your fasting and eating windows from your chosen method and start time. It tells you when your fast ends, when you can eat, and when the eating window closes — so you can plan your day. It focuses purely on timing.
Popular fasting methods
Method
Fast
Eat
14:10
14 h
10 h
16:8 (most common)
16 h
8 h
18:6
18 h
6 h
20:4 (Warrior)
20 h
4 h
OMAD
23 h
1 h
For 16:8, finishing your last meal at 8:00 PM means your eating window opens at 12:00 PM the next day and closes again at 8:00 PM.
How to use the intermittent fasting calculator
Pick your method (or set custom fasting hours).
Enter the time you finish your last meal.
Read your eating window open and close times.
Tips for intermittent fasting
Stay hydrated — water, plain tea and black coffee are usually fine during a fast.
Eat balanced meals in your window rather than overcompensating.
Ease in — start with a shorter fast like 14:10 and adjust.
Listen to your body — stop or seek advice if you feel unwell.
Intermittent Fasting FAQ
How do I calculate my fasting window?
Choose a fasting method, such as 16:8, and enter the time of your last meal. The calculator adds the fasting period to determine when your eating window opens, then applies the eating window length to find when it closes.
What is 16:8 intermittent fasting?
The 16:8 method involves fasting for 16 hours and eating within an 8-hour window each day. For example, if your last meal is at 8 PM, your next meal would typically be at 12 PM the following day, with your eating window ending at 8 PM.
What’s the difference between this and a fasting timer?
This calculator helps plan your fasting and eating schedule by showing when each window begins and ends. A fasting timer is designed to track a fast that’s already in progress with a live countdown.
Can I drink anything while fasting?
Water, plain tea and black coffee are generally considered acceptable during a fast because they contain little or no calories. Drinks containing calories would typically break the fast.
Is intermittent fasting safe?
Intermittent fasting works well for many people but is not suitable for everyone. It is generally not recommended during pregnancy, for people with a history of disordered eating, or for some individuals with diabetes or certain medical conditions. Consult a healthcare professional before starting.
Is the intermittent fasting calculator free?
Yes, this intermittent fasting calculator is completely free, requires no sign-up, and provides instant results directly in your browser. It is intended for informational purposes only and is not medical advice.
