Adults typically need between 10% and 25% of their total sleep time to be deep sleep, which is roughly 40 to 120 minutes (about 1 to 2 hours) per night if they get the recommended 7 to 9 hours of overall sleep. Deep sleep is essential for physical recovery, immune system strengthening, and brain function. The exact amount can vary by age, overall sleep duration, and individual needs, but feeling refreshed during the day is a good indicator of sufficient deep sleep.

Recommended Deep Sleep Duration

• Adults spend about 10–25% of their sleep in deep sleep.
• For 7 hours of sleep, deep sleep should be about 42 to 105 minutes.
• For 8 hours of sleep, deep sleep should be about 48 to 120 minutes (1 to 2 hours).

Why Deep Sleep Matters

• It supports muscle recovery, tissue growth, and immune health.
• Brain waves slow significantly, and the heart and respiratory rates decrease.
• The body regenerates most intensively during this stage.

Variation With Age and Individual Differences

• Children and teenagers need more deep sleep than adults due to growth.
• Deep sleep decreases with age, typically reducing by about 1.7% per decade.
• Women may spend slightly more time in deep sleep than men.

Getting at least 1 to 2 hours of deep sleep per night, aligned with total sleep recommendations, helps maintain health and daily functioning.