Fasting Window Calculator

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⏰

Calculate your eating window based on your intermittent fasting protocol

Fasting Protocol

Time of Your First Meal

The time you break your fast with your first meal

Fasting

8:00 PM

16h fast 8h eat

Eating

8:00 PM

Your eating window

12:00 PM → 8:00 PM

Stop Eating By

8:00 PM

16:8 — 16h Fast, 8h Eating — First meal at 12:00 PM

Protocol Comparison

<tr class="font-semibold bg-(--color-accent-health)/5"> <td class="py-1.5 pr-3 text-(--color-accent-health)">16:8 ✓</td> <td class="py-1.5 pr-3">16h</td> <td class="py-1.5 pr-3">8h</td> <td class="py-1.5 pr-3">8:00 PM</td> <td class="py-1.5">Easy</td> </tr><tr class=""> <td class="py-1.5 pr-3 text-(--color-text-primary)">18:6</td> <td class="py-1.5 pr-3">18h</td> <td class="py-1.5 pr-3">6h</td> <td class="py-1.5 pr-3">6:00 PM</td> <td class="py-1.5">Moderate</td> </tr><tr class=""> <td class="py-1.5 pr-3 text-(--color-text-primary)">20:4</td> <td class="py-1.5 pr-3">20h</td> <td class="py-1.5 pr-3">4h</td> <td class="py-1.5 pr-3">4:00 PM</td> <td class="py-1.5">Hard</td> </tr>

Protocol	Fast	Eating Window	Stop Eating	Difficulty

💡

Pro tip: Black coffee, plain tea, and water don't break your fast. Consistency matters more than the specific protocol — pick one that fits your lifestyle.

Intermittent Fasting Guide

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16:8 (Leangains)

Most popular protocol. 16-hour fast with an 8-hour eating window. Great for beginners — skip breakfast, eat between 12 PM and 8 PM.

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18:6

Intermediate protocol with 18-hour fast and 6-hour eating window. Often a natural progression from 16:8 for experienced fasters.

🔥

20:4 (Warrior Diet)

Advanced protocol. 20-hour fast with a 4-hour eating window, typically one large meal in the evening. Not recommended for beginners.

💡 Tips for Success

Stay hydrated — water, black coffee, and unsweetened tea don't break your fast
Start gradually — begin with 12:12 or 14:10, then work up to 16:8 over 1–2 weeks
Eat nutrient-dense meals — prioritize protein, healthy fats, and fiber during your eating window
Listen to your body — if you feel dizzy, weak, or extremely hungry, break your fast early
Stay consistent — aim for the same eating window daily to regulate your circadian rhythm
Electrolytes matter — add a pinch of salt to your water if you experience headaches during extended fasts

📊 Protocol Comparison

Protocol	Fasting	Eating	Best For	Autophagy
16:8	16 hours	8 hours	Beginners, weight maintenance	Mild
18:6	18 hours	6 hours	Weight loss, intermediate	Moderate
20:4	20 hours	4 hours	Deep autophagy, advanced	Strong

⚠️ Important: Intermittent fasting is not recommended for pregnant or breastfeeding women, individuals with a history of eating disorders, those with diabetes (especially Type 1), or people on certain medications. Always consult a healthcare provider before starting any fasting regimen.