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.

For most people, drifting off takes about 10 to 20 minutes. Falling asleep the instant your head hits the pillow is not the goal it sounds like.

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.