Most healthy adults need around 1–2 hours of deep sleep per night, which usually works out to roughly 15–25% of total sleep time (assuming 7–9 hours in bed).

Deep sleep targets by age

  • Adults 18–64 : Aim for 7–9 hours of total sleep, with about 55–110 minutes of deep sleep (roughly 13–23% of the night).
  • Older adults 65+ : Often sleep 7–8 hours, with ~45–90 minutes of deep sleep as deep stages naturally decline with age.
  • Deep sleep tends to be concentrated in the first half of the night, especially the first 1–2 sleep cycles.

Why deep sleep matters

Deep (slow‑wave) sleep is when the body does a lot of physical repair work and immune system maintenance.

It supports memory consolidation, hormone balance, and helps you wake feeling physically restored rather than heavy and foggy.

When to worry

  • Regularly getting less than about 40–60 minutes of deep sleep despite 7+ hours in bed can leave you tired, sore, and mentally dull.
  • If a tracker shows very low deep sleep and you also snore loudly, gasp, or wake unrefreshed, that is a good reason to talk with a doctor or sleep specialist.

Quick ways to support deep sleep

  • Keep a consistent sleep schedule (even on weekends).
  • Cool, dark, quiet bedroom; avoid heavy screens and intense work right before bed.
  • Limit late caffeine and alcohol, which both reduce deep sleep quality.

If you share your age, typical sleep duration, and what your tracker reports, a more tailored “is this okay?” range can be sketched out.