Most adults need 7 to 9 hours of daily sleep to function at their best. Odds are, you do too.
Your Alertness or Effectiveness Score will take into consideration ALL sleeps, but it is best to get at least one single sleep of at least 6 or 7 hours, and top up with naps if you need to. For proper health, safety and performance one 8-hour sleep is better for you than two 4-hour sleeps.
Best: One single long sleep of 7+ hours - ensures better recovery from the day, including maximizing reaction time and consolidating learnings and memories.
Better, but not ideal: Two separate sleeps totaling 8 hours. Better than no sleep or one short sleep, but not long enough in one to ensure optimal recovery through the full range of recovery processing that your brain needs to complete
Not enough sleep: One short sleep totaling just over four hours will not be enough to fully recover from your day or night and prepare you for the next. If you can sleep longer in one go, you should! If it’s not possible, top up with a nap or second sleep.