What Is a Sleep Compatibility Score? (And How to Improve Yours)

A Metric Built for Two

A sleep compatibility score is something that simply cannot exist in an individual sleep tracking app. It requires data from both partners, collected simultaneously, and then analysed for the degree of alignment across multiple dimensions of sleep. SleepTwo calculates this score every night for couples who both wear Apple Watch to bed, and it has become one of the most talked-about features among the app's users.

But what does the score actually measure? And once you have it, what can you actually do to improve it?

What Goes Into the Score

SleepTwo's compatibility score is a composite metric built from several components, weighted to reflect their relative impact on joint sleep quality.

Sleep timing overlap. The most heavily weighted component. It measures what percentage of each partner's total sleep time is shared — the window when both people are simultaneously asleep. Higher overlap is associated with better sleep quality for both partners and stronger relationship satisfaction in the research literature.

Sleep duration symmetry. This reflects how closely matched both partners' total sleep time is on a given night. A large discrepancy — one person sleeping six hours while the other gets nine — suggests significant schedule misalignment, even if there is some timing overlap.

Sleep stage synchrony. A more nuanced component that looks at whether both partners are moving through similar sleep stages at similar times. Couples who enter deep sleep and REM sleep in close proximity tend to disturb each other less and experience better individual sleep quality.

Movement and disruption. This component captures the degree to which one partner's movements are associated with sleep disruption events in the other. High movement scores in one partner that coincide with increased awakenings in the other will lower the compatibility score.

The result is a single number on a 100-point scale that provides an at-a-glance picture of how well a couple slept together on any given night.

What a Good Score Looks Like

In practice, most couples starting with SleepTwo score in the 55 to 75 range during their first week. This is normal and should not be discouraging — it reflects the reality that most couples have not actively optimised their sleep as a shared system. Couples who have been actively managing their sleep habits together tend to score in the 75 to 90 range consistently.

Scores above 90 are uncommon on weeknights due to the natural variation introduced by work schedules, stress, and the variability of sleep itself. They are more common on weekends or vacation, which is itself informative.

How to Improve Your Score

The most impactful lever for most couples is sleep timing — specifically, narrowing the gap between when each partner falls asleep and when they wake up. If one partner consistently goes to bed 90 minutes later than the other, that alone will cap the compatibility score because 90 minutes of each night is spent in misaligned sleep.

Practical approaches to narrowing the timing gap include: agreeing on a shared target bedtime and working toward it incrementally; the later-chronotype partner reducing blue light exposure earlier in the evening to advance their melatonin onset; and the earlier-chronotype partner resisting the urge to get up significantly before the other on weekends.

The second most impactful lever is the bedroom environment. A room that is too warm, too light, or insufficiently quiet increases movement and fragmentation in both partners, reducing stage synchrony and raising the disruption component of the score.

Sending a Bedtime Bridge goodnight message through SleepTwo before sleep is a small habit that many users report correlating with higher scores — likely because it creates a settled, warm closing to the day that reduces pre-sleep anxiety for both partners.

Start Tracking Tonight

SleepTwo is the only sleep app built specifically for couples. Download it free, pair with your partner in under 2 minutes, and wake up to your first compatibility score tomorrow morning. Together Pro covers both of you.