Nap Timer

About 20 minutes is where most sleep advice lands. The Sleep Foundation suggests about 20 minutes, and no more than 30, for adults. Past 30 minutes you are more likely to reach deep sleep, and waking from deep sleep is what leaves you groggy. That grogginess is called sleep inertia.

In a 2006 study by Brooks and Lack, 24 young adults who were short on sleep took afternoon naps of 5, 10, 20 and 30 minutes. The 10-minute nap made them more alert straight away. After 20 minutes the benefit showed up about 35 minutes later, and the 30-minute nap brought a spell of grogginess first.

A 90-minute nap is the other common choice. An average sleep cycle lasts about 90 minutes, so a nap that long covers roughly one full cycle.

The timer counts from the moment you press Start nap, not from when you fall asleep. The naps in that study counted minutes of actual sleep, so add the few minutes you usually take to drift off.

Wake up at shows when the alarm will ring, in your own clock format, so you can check it fits before you lie down. The Sleep Foundation suggests napping eight or more hours before bedtime, which for most people means before 3pm.

The alarm is a soft bell: three notes taking turns every 3 seconds. It starts quiet and grows louder over the first 15 strikes, about 45 seconds, then rings for about 3 minutes and stops. That makes it gentle, and it also makes it the wrong alarm to trust for a flight.

Press Test alarm before you lie down to check you can hear it. Background volume sets only the background noise. The bell has its own level, so set your device volume loud enough for the bell. If you picked a Background sound, it fades out over the last 20 seconds before the bell.

The countdown runs from the clock, so it stays right when you switch tabs. While it runs, the page asks your browser to keep the screen on. Phones can still pause sound in the background, and a paused phone rings late or not at all, so leave this tab open with your sound on. On Android the phone also vibrates when the bell starts.

Nap timer gets about 8,100 searches a month in the US, according to Google's Keyword Planner. A nap video is a simple format to add to a music channel: 20 or 30 minutes of calm sound, with the length in the title so people can find the one they want.

Chillframe makes the calm music or ambience, the visual and the finished video at the length you set, from a minute up to an hour, and publishes it to YouTube on the days you pick. It doesn't add a wake-up bell, so the video ends when the sound does.