Nap length refers to the duration of a short sleep taken during the day, typically lasting anywhere from 10 to 30 minutes. This brief rest can help improve alertness, mood, and cognitive performance without causing sleep inertia, which is the grogginess that can occur after longer sleep periods. Longer naps, usually over 30 minutes, can lead to deeper sleep stages, making it harder to wake up feeling refreshed. The ideal nap length varies by individual needs and schedules, but many people find that a 20-minute nap strikes a good balance between rest and alertness.