Sleep Age: How old does your sleep look?

Your age keeps going up. Your sleep doesn't have to.

Sleep Age turns your recent sleep patterns into an age, giving you a simple way to see how your sleep is doing.

If you're 32 and your Sleep Age is 27, it means your recent sleep looks more like that of people around 27, based on several sleep-related measures.

It looks at your overall pattern, not just one or two nights.

What it looks at

Sleep Age is based on four things:

Resting heart rate

Your heart rate during the lowest stretch of the night. It reflects longer-term physical condition and can also be affected by exercise, weight, alcohol, and stress.

Sleep duration

How long you actually sleep each night.

Sleep regularity

How consistent your bedtime is.

Sleep efficiency

How much of your time in bed you actually spend asleep.

Resting heart rate is compared with people of the same age and sex. Duration, regularity, and efficiency are compared with typical levels across the population. The four are then combined into your Sleep Age.

In the details, you can also see how much each measure is moving your Sleep Age up or down.

Deep sleep and heart rate variability matter too, and you can find them in Sleep & Recovery. But there isn't yet enough reliable research to consistently translate them into an age, so they don't directly contribute to Sleep Age.

How much sleep does it look at?

Sleep Age uses your most recent 84 valid sleep nights, or about 12 weeks.

As each new valid night comes in, the oldest one drops out. This keeps Sleep Age focused on your recent pattern instead of letting one unusually good or bad night move it too much.

Your first Sleep Age appears after 7 valid nights. It then updates weekly. Once you have 84 nights, the full 12-week window makes the result more stable.

Nights without sleep data aren't filled in or counted as bad sleep.

Why does the reference differ from person to person?

The same number can mean different things at different ages.

For example, a resting heart rate of 62 bpm can represent a different position in the population for someone who is 25 than for someone who is 55.

That's why resting heart rate uses reference distributions based on your age and sex, rather than applying one standard to everyone.

What happens if you change devices?

Different devices measure sleep in different ways.

That's why Apple Watch and Oura data aren't simply combined. When you switch to a new device, mellows builds your Sleep Age from that device's data.

This helps keep changes in Sleep Age tied to your sleep, rather than to differences between devices.

How should you read your Sleep Age?

Don't focus too much on a single number.

What matters more is the direction it takes over time.

Moving gradually from 36 to 33, then to 31, tells you more than seeing a particularly good number for one week.

Sleep Age isn't a fixed label, either.

Sleep duration, regularity, and efficiency can change with your everyday habits. Resting heart rate reflects longer-term physical condition, so it usually takes more time to shift.

Your age keeps moving forward. Your sleep doesn't have to.