Coffee Nap Timing Calculator

How it is calculated

Enter coffee_time as a 24-hour clock time (HH:MM), nap_minutes as the planned nap length and onset as the minutes the caffeine takes to start working for you.

nap end = coffee_time + nap_minutes
caffeine peak = coffee_time + onset
gap = |onset − nap_minutes|

The clock wraps around midnight, so 23:50 plus 20 minutes shows 00:10. The nap length must be between 5 and 45 minutes and the onset between 10 and 60 minutes, otherwise there is no result. The time must be written with a colon and no seconds; "14.10" or "14:10:00" gives no result. The gap is an absolute number of minutes, so it does not say whether you wake before or after the peak: compare the two clock times for that. The onset is your own assumption; the tool does not know your caffeine sensitivity.

Common mistakes

• Counting the nap from when you lie down rather than from when you finish the coffee. The clock starts at the time you enter, so enter the moment you drink it.
• Typing 12-hour times with am or pm. The field expects 24-hour HH:MM, so 2:10 pm must be entered as 14:10; 2:10 alone is read as 02:10 at night.
• Reading the gap as how groggy you will feel. It is only the difference in minutes between wake-up and the assumed caffeine onset; it carries no sign, so a 30-minute nap with a 20-minute onset also shows 10 min.
• Forgetting that falling asleep takes time. If it takes 5 minutes to drift off, your real sleep is shorter than the nap length you entered.
• Entering a nap of 60 or 90 minutes, or an onset under 10 minutes. Nap length outside 5–45 and onset outside 10–60 give no result.