Short answer: Healthy adult sleep is made of repeating ~90-minute cycles through three kinds of sleep: light sleep (about 50–60% of the night), deep sleep (about 15–20%), and REM sleep (about 20–25%). You don't choose how much of each you get directly — but getting enough total sleep (7–9 hours) on a consistent schedule, in a cool, dark room, is how you maximize the restorative deep and REM stages.
Your Night Is Built From Cycles
Sleep isn't one flat state — it's a structured journey. Over a normal night you move through four to six sleep cycles, each lasting roughly 90 minutes. Within every cycle you pass through lighter and deeper stages and into REM. Crucially, the mix shifts as the night goes on: deep sleep dominates the early cycles, while REM gets longer in the second half of the night — which is exactly why a cut-short morning robs you of REM.
The Three Types of Sleep, and What Each Does
Light sleep (~50–60% of the night)
This is the transitional stage where your heart rate and body temperature drop and your muscles relax. It's easy to dismiss as "just" light sleep, but it's where your brain begins consolidating memories and your body starts to recover. It's also the bridge into the deeper stages — you can't get deep sleep without passing through it.
Deep sleep (~15–20% of the night)
Also called slow-wave sleep, this is the most physically restorative stage — roughly 60 to 100 minutes across a typical 8-hour night. During deep sleep your body repairs tissue, strengthens the immune system, and clears metabolic waste from the brain. This is the sleep that makes you feel physically restored. It's hardest to wake someone from deep sleep, and being pulled out of it is what causes that heavy, groggy feeling.
REM sleep (~20–25% of the night)
REM (rapid eye movement) is when most vivid dreaming happens and your brain is highly active. It's essential for learning, memory consolidation, and emotional processing. Because REM concentrates in the later cycles, the last few hours of sleep are disproportionately valuable — sleeping six hours instead of eight doesn't cost you 25% of your REM, it can cost you much more.
How Much Do You Actually Need?
Most adults need 7 to 9 hours of total sleep. If you hit that consistently, the healthy percentages of deep and REM tend to take care of themselves — your body is remarkably good at prioritizing the stages it needs. Rather than chasing a specific "deep sleep number" on a tracker, aim for enough total sleep, regular timing, and good conditions, and let your brain handle the architecture.
How to Get More Restorative Sleep
You can't force a particular stage, but you can remove the things that fragment it and add the things that protect it:
- Protect your total sleep time. The single biggest lever — especially for REM — is simply not cutting the night short.
- Keep a consistent schedule. Regular sleep and wake times stabilize your cycles so you move through stages efficiently.
- Keep the room cool and dark. A cooler core temperature supports deep sleep; complete darkness protects the REM-rich morning hours from being cut short by light.
- Avoid alcohol and late caffeine. Both fragment sleep architecture — alcohol suppresses REM early and disrupts the second half of the night.
- Support sleep onset and relaxation. Falling asleep faster and staying calm means more uninterrupted cycles.
Where Sleeps Fits In
You can't supplement your way to a specific sleep stage — but you can support the conditions that let your stages run their full course. The Powder pairs magnesium glycinate, which supports muscle relaxation and a calm nervous system, with glycine, which helps lower core body temperature for faster sleep onset — both useful for settling into cycles smoothly. And because REM concentrates in the final hours, The Mask protects that fragile morning sleep by keeping early light out.
Frequently Asked Questions
How much deep sleep do I need per night?
Roughly 15–20% of total sleep, or about 60–100 minutes across an 8-hour night for most adults.
How long is one sleep cycle?
About 90 minutes, and you typically go through four to six cycles per night.
Why is the second half of the night important?
REM sleep gets longer in later cycles, so cutting your night short disproportionately reduces REM — the stage tied to memory and emotional processing.
Should I trust the deep-sleep number on my smartwatch?
Consumer trackers estimate stages and aren't perfectly accurate. Use the trend as a rough guide, but prioritize total sleep, consistency, and how you feel.
The Bottom Line
Light, deep, and REM sleep each play a distinct role, and they unfold in a predictable rhythm across the night. You don't need to micromanage the percentages — you need enough total sleep, on a steady schedule, in cool darkness. Do that, and the restorative stages fall into place.
Give your cycles the best shot with The Powder for calm, faster sleep onset and The Mask to guard your REM-rich morning hours.