Sleep Index explained: how the Ring scores your night

What is Sleep Index?

Sleep Index runs from 0 to 100. Higher scores mean adequate duration, efficient and uninterrupted sleep, enough time in restorative stages, timing aligned with your own rhythm, and overnight vitals pointing toward recovery.

It's calibrated so that:

• 70 to 85 is a solid night for most adults
• Above 85 is an unusually restorative night
• Consistently below 60 suggests something in how your sleep is structured, or in your habits, is regularly falling short.

The Sleep Index appears on the sleep card each morning, with the breakdown underneath: total sleep time, efficiency, and the split across light, deep and REM.

It also feeds your Recovery Score. A high Sleep Index raises the sleep contributor to that score, and a low one pulls it down and adjusts how much the app suggests you take on that day.

Read it as a trend rather than a daily verdict. Night-to-night variation is normal. What matters is whether the 7- or 14-night average is drifting, and which dimension is driving it.

How Sleep Index is calculated

The Ring records your heart rate and its beat-to-beat variation, your movement, and your skin temperature. It uses those to map your night into sleep stages (wake, light, deep and REM) without EEG, then scores five dimensions.

• Duration: How long you slept, measured against age-based targets. The American Academy of Sleep Medicine recommends at least 7 hours a night for adults aged 18 to 60.
• How settled the night was: How much of your time in bed you actually spent asleep, and how often sleep was broken by waking.
• Restorative sleep: Time spent in REM and deep sleep stages, for physical repair and consolidating memory.
• Timing: Alignment with your recent sleep/wake.
• Overnight vitals: A heart rate that drops low and bottoms out early and skin temperature close to your own baseline.

What the research says about sleep quality

Sleep quality isn't one thing. How long you sleep, how broken it is, which stages you get and when you sleep all matter separately. That's why a single figure for hours tells you so little.

Around seven hours is the healthiest amount: Pooling studies that followed people for years, the risk of dying early or developing heart disease was lowest at about seven hours a night. It rose in people who slept less, and in people who slept considerably more.

A bad night shows up in your body the next morning: In adults who struggle to fall asleep, the heart hadn't recovered as well by morning as it had in good sleepers.

Your temperature drop and your heart rate are connected: Your body normally cools before you fall asleep. When that cooling is weaker, heart rate runs higher through every stage of the night. That's why the Ring reads the two together rather than separately.

Skin temperature follows your body clock, not the room: In a wearable study of over 20,000 people, skin temperature rhythms tracked sleep timing even during naps.

What’s a normal Sleep Index score?

Across 353,737 members recording valid nights between January and May 2026, the median Sleep Index was 80. Half of all nights land between 72 and 85, with a long tail of lower-scoring nights pulling the average down to 76.7.

How to get the perfect Sleep Index score

For most members, the biggest gains come from timing regularity.

The importance of the consistent timing dimension is grounded in Ultrahuman's own research on sleep regularity and glucose, which found steadier night-to-night sleep timing tracks with steadier overnight glucose.

Winding down and maximizing deep sleep will also have a big impact on your Sleep Index.