Source: Wikipedia

Sleep is divided into several phases, including REM and deep sleep. We progress through these stages in cycles, each complete cycle taking on average 90 minutes. There is huge difference about how we feel after waking up depending on the stage we are in at the moment. We feel most refreshed waking up at the top of the cycle, whereas if the alarm clock wakes us up from deep sleep, we may feel groggy and not well rested, no matter how long we slept.

Using the calculator below you can calculate the right length of sleep in order to wake up right at the top of the cycle. It works best with gentle alarms, like a wake up lamp or quietly playing music. Still, if you need to be sure you won't oversleep, it's best to have a solid loud alarm (or a wake up call) set for later.

Of course this is a rough estimate, but it might be worth to try; be sure to let us know in the comments if it worked for you! We'd also appreciate any tips on sleeping better, waking up early, natural sleep aids etc.

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