Intermittent Fasting Calculator
Calculate your eating window, fasting window, and daily fasting schedule for 16:8, 18:6, 20:4, and other IF protocols.
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How to use this calculator
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Select your intermittent fasting protocol (16:8 is the most popular starting point).
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Enter the time you want to start eating each day.
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Choose your goal to get goal-specific tips.
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Review your eating window and fasting window.
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Drink plenty of water, black coffee, or plain tea during your fasting hours.
Frequently asked questions
What is the best intermittent fasting protocol for beginners?
Start with 14:10 or 16:8. The 16:8 protocol — 16 hours fasting, 8 hours eating — is the most studied and sustainable. A common approach is skipping breakfast (eating from 12pm–8pm). 18:6 and 20:4 are more advanced. OMAD (one meal a day) is very restrictive and not recommended without experience.
Does coffee break intermittent fasting?
Black coffee (no milk, cream, or sugar) does not break a fast in terms of insulin response and can actually enhance fat burning by boosting ketone production. Adding milk, cream, flavoured syrups, or sweeteners — even calorie-free sweeteners — may stimulate an insulin response and could break a fast for strict protocols.
Can I exercise while fasting?
Yes — many people exercise during fasted states to enhance fat burning. Light to moderate exercise is fine fasted. For intense workouts or strength training, some prefer to eat beforehand or have BCAAs (branched-chain amino acids). Listen to your body — if you feel dizzy or weak, eat first.
Will intermittent fasting cause muscle loss?
Short fasting windows (up to 24 hours) do not cause meaningful muscle loss if you consume adequate protein in your eating window. Research shows IF combined with resistance training and sufficient protein (1.6–2.2g/kg bodyweight) preserves muscle mass while reducing fat. Prolonged fasting (2+ days) without protein can be catabolic.
Intermittent Fasting Calculator — Plan Your Eating Window
16:8 vs 18:6 vs 20:4 — which protocol is right for you?
16:8 is the gold standard for beginners and sustainable long-term. Skip breakfast, eat from noon to 8pm. 18:6 (eat 12pm–6pm) adds hunger management benefits and deeper ketosis. 20:4 (Warrior Diet — eat 4pm–8pm) is aggressive and harder to maintain socially. 5:2 is ideal for people who don't want to fast daily. OMAD suits experienced fasters with specific goals. Start conservative — you can always extend your fast as you adapt.
Health benefits of intermittent fasting
Research supports IF for: weight loss and fat reduction (especially visceral fat), improved insulin sensitivity and blood sugar control, reduced inflammation markers, improved cardiovascular risk factors (blood pressure, cholesterol), cellular autophagy (cleaning damaged cells), and potential longevity benefits. Most benefits begin appearing after 4–8 weeks of consistent practice. IF is a tool — it works best combined with a nutritious diet, not as a substitute for one.
Learn more from an authoritative source:
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Results are estimates for informational purposes only and do not constitute professional financial, medical, legal, or technical advice. Read full disclaimer →