Coffee Nap Timing Calculator

About this calculator

A coffee nap works by stacking two separate ways of fighting sleepiness so they hit at the same moment: drinking coffee just before a short nap, then waking up right as the caffeine kicks in. Caffeine takes roughly 20 to 30 minutes to be absorbed and reach a noticeable level in the bloodstream, which happens to be almost exactly how long sleep scientists recommend for a short, alertness-boosting nap, long enough to clear some adenosine (the chemical that builds up in the brain and makes you feel drowsy) but short enough to avoid deep sleep and the grogginess of sleep inertia.

The trick, popularised among shift workers, long-distance drivers and students cramming for exams, is timing: if the nap runs too long you wake up groggy despite the caffeine, and if it's too short the caffeine hasn't kicked in yet, so the two effects miss each other instead of combining.

Enter the time you drink your coffee and how long you plan to nap, and this calculator shows how well your timing lines up with caffeine's absorption window.