Sleep guides

Guides behind the tools

Short, sourced explainers for the questions our calculators raise — written in plain language and kept within general wellness guidance.

Are sleep cycles really 90 minutes?

Ninety minutes is a useful planning average, not a fixed rule. Real cycles run shorter or longer and shift across the night.

Set your own fall-asleep time and work backward from your alarm to a realistic bedtime.

The hours you spend in bed are your sleep opportunity. The hours you are actually asleep are usually fewer — and the gap is normal.

Going to bed and waking at similar times most days is one of the simplest, most reliable ways to support steady sleep.

Cycle-timing tools are good for planning enough sleep. They cannot guarantee how rested you will feel — and it is worth knowing why.