Intermittent Fasting Calculator: Schedule Guide
Intermittent fasting (IF) is an eating pattern that cycles between periods of eating and fasting. Our Intermittent Fasting Calculator helps you plan your schedule for any protocol.
Popular Fasting Protocols
| Protocol | Fasting | Eating | Best For |
|---|---|---|---|
| 12:12 | 12 hours | 12 hours | Beginners |
| 14:10 | 14 hours | 10 hours | Easy start, women often prefer this |
| 16:8 | 16 hours | 8 hours | Most popular, good balance |
| 18:6 | 18 hours | 6 hours | Intermediate, faster results |
| 20:4 | 20 hours | 4 hours | Advanced, significant fat loss |
| OMAD | 23 hours | 1 hour | One meal a day, experienced fasters |
How to Choose Your Protocol
Beginners (Start Here)
12:12 or 14:10 — Simply skip late-night snacking and delay breakfast. For example, eat from 8:00 AM to 8:00 PM (12:12) or 10:00 AM to 8:00 PM (14:10).
Most Popular
16:8 — Eat from 12:00 PM to 8:00 PM. Skip breakfast, eat lunch and dinner. This is the most sustainable protocol for most people.
Advanced
18:6 or 20:4 — Eat from 2:00 PM to 8:00 PM (18:6) or 4:00 PM to 8:00 PM (20:4). Requires adaptation and careful meal planning.
One Meal a Day
OMAD — Eat one large, nutrient-dense meal. Not recommended for beginners, pregnant women, or those with eating disorder history.
What You Can Drink During Fasting
✅ Allowed (zero calories):
- Water (still or sparkling)
- Black coffee (no milk, no sugar)
- Unsweetened tea (green, black, herbal)
- Apple cider vinegar (1 tsp in water)
❌ Breaks the fast:
- Any food
- Milk or cream in coffee/tea
- Juice
- Bone broth (has calories)
- Sugar-sweetened beverages
The Science Behind Intermittent Fasting
Insulin Reduction
Fasting keeps insulin levels low, which signals your body to burn stored fat for energy.
Autophagy
After 16+ hours of fasting, your body begins autophagy — a cellular cleanup process that removes damaged cells and may protect against aging and disease.
Human Growth Hormone (HGH)
Fasting can increase HGH levels by 5×, supporting muscle preservation and fat burning.
How to Break Your Fast
- Start with protein and fiber — Eggs, lean meat, vegetables
- Avoid sugar and refined carbs — Prevents blood sugar spikes
- Eat slowly — Your digestive system needs time to wake up
- Stay hydrated — Continue drinking water with meals
Common Mistakes to Avoid
- Overeating during the window — IF is not a license to eat anything
- Not getting enough protein — Aim for 1.6–2.2 g/kg body weight
- Starting too aggressively — Begin with 12:12 before jumping to 16:8
- Ignoring hunger cues — If you feel dizzy or unwell, eat
Calculate your calorie needs → Plan your macros → Stay hydrated →
Is Intermittent Fasting Safe?
Generally safe for: Healthy adults, people with stable weight, those who prefer time-restricted eating
Consult a doctor if you are: Pregnant or breastfeeding, diabetic (especially on medication), have a history of eating disorders, underweight, or taking medications that require food