What is sleep efficiency and what should mine be?

Sleep efficiency is the ratio of time actually sleeping to time spent in bed, expressed as a percentage, healthy sleep efficiency in adult men is above 85%, and persistent sleep efficiency below 80% (meaning you are awake for more than 20% of your time in bed) indicates fragmented sleep architecture that increases cardiovascular and metabolic risk (Ohayon et al., Sleep, 2004).

Sleep efficiency is distinct from total sleep time. A man who spends 9 hours in bed but is awake for 2 of them has 78% sleep efficiency, worse than a man who spends 7.5 hours in bed and sleeps 6.8 of them (91% efficiency). Wearables report sleep efficiency (sometimes under labels like "sleep score" or "efficiency index"), but they modestly overestimate it because they score quiet lying-still periods as sleep. If your device reports 85% efficiency but your partner says you toss frequently, the actual number may be lower.

Honesty Scale: Solid (1) for sleep efficiency as a clinical metric. Wearable accuracy for this specific metric is Promising (2).

What to do: A sleep efficiency consistently below 80% is a clinical signal. Common causes: sleep apnea (the most important to rule out), excessive time in bed (counterproductive, spending 10 hours in bed trying to sleep 8 hours often lowers efficiency), anxiety, and temperature issues. Cognitive behavioral therapy for insomnia (CBT-I), including sleep restriction protocols, is the most evidence-supported treatment for chronic low sleep efficiency.

For the full picture, read The Sleep Architecture Deep Dive