Earlier window · 10 AM–4 PM
- 10 AM · Roasted chicken plate
- 1 PM · Yogurt, banana and almonds
- 3 PM · Salmon and sweet potato
Free window calculator
18:6 intermittent fasting
18:6 means fasting for 18 hours each day and eating within a 6-hour window. For example, eat from noon to 6 PM, then fast from 6 PM until noon the next day.
Choose your intermittent fasting windows
Eat · 6 hours12:00 PM → 6:00 PM
Fast · 18 hours6:00 PM → 12:00 PM (next day)
The eating window closes when the fasting window begins. These are repeating clock schedules, not elapsed-time timers across daylight saving changes. Switching modes compares duration only.
Your choices stay in this calculator’s memory. They are not sent or saved; reloading resets them. No account needed.
18 hour fast vs. 16:8 and 20:4
Only the lengths of the windows change here. The comparison does not rank health outcomes or recommend a mode.
| Mode | Eating | Fasting |
|---|---|---|
| 16:8 | 8 hours Noon–8 PM | 16 hours Until noon next day |
| 18:6 | 6 hours Noon–6 PM | 18 hours Until noon next day |
| 20:4 | 4 hours Noon–4 PM | 20 hours Until noon next day |
Two ways to arrange an 18:6 day
Each example has two meals and a snack, finished before the window closes. The same foods illustrate an earlier or later schedule. These portions are examples, not a daily calorie target or a personalized meal plan.
Later window · noon–6 PM
- Noon · Roasted chicken plate
- 3 PM · Yogurt, banana and almonds
- 5 PM · Salmon and sweet potato
What is in the example meals?
Calculated calories use the USDA entries linked below. Weighed portions match the listed preparation state. Add any oil, sauces, drinks or other foods separately.
Roasted chicken plate
- Chicken breast (roasted) · 150 g · 248 kcal
- Sweet potato (baked) · 250 g · 225 kcal
- Avocado · 100 g · 167 kcal
Calculated: 248 + 225 + 167 = 640 kcal (sum of displayed ingredients).
Yogurt, banana and almonds
- Greek yogurt · 170 g · 100 kcal
- Banana · 120 g · 107 kcal
- Almonds · 30 g · 174 kcal
Calculated: 100 + 107 + 174 = 381 kcal (sum of displayed ingredients).
Salmon and sweet potato
- Salmon · 150 g · 309 kcal
- Sweet potato (baked) · 250 g · 225 kcal
- Avocado · 100 g · 167 kcal
Calculated: 309 + 225 + 167 = 701 kcal (sum of displayed ingredients).
Example day: 1722 kcal, calculated by adding the displayed meal totals. This is not a recommended intake.
For more combinations and portions, explore our meal plans and low calorie meal ideas.
18 hour fast benefits, suitability and side effects
Consult a doctor before starting intermittent fasting.
How long should I do intermittent fasting?
This calculator displays one repeating day. It does not set a number of weeks or an end date. Consult a doctor before starting.
Keep track of the meal you actually eat.
KaloCam helps you start a food log from a photo, review the estimated calories and macros, and keep track of your meals. Photos cannot measure exact portions or hidden oil; review the estimate before saving.
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Sources and calculation method
Food values come from the existing food pages’ cached USDA FoodData Central records. For each ingredient: USDA kcal per 100 g × listed grams ÷ 100. Round each ingredient to an integer, then add those displayed values for each meal and day. Gram weights are whole numbers. Values are calculated estimates.
Health evidence: the Johns Hopkins Medicine article request was blocked (HTTP 403) on October 28, 2026. No article text was available for verification, so no health benefit, contraindication or side-effect claims are included here.
Prepared by the KaloCam team · October 28, 2026. This schedule tool provides general information, not medical advice.