The best temperature for sleep

The ideal: about 18 °C (65 °F)

For most adults the sweet spot is around 18 °C (65 °F), within a workable range of roughly 16–20 °C (60–68 °F). It sounds cool, but that's the point: a cooler room helps your body do what it needs to do to sleep.

Why cool sleep works

Falling asleep requires your core temperature to drop by about 1 °C. Your body does this naturally in the evening by sending heat out to your hands and feet. A cool bedroom speeds that heat loss, so you fall asleep faster and spend more time in deep, slow-wave sleep. A room that's too warm does the opposite — studies show temperatures above ~24 °C noticeably increase wakefulness and reduce sleep quality.

How to get there

• Set the thermostat low and use warm bedding for comfort — control warmth with blankets, not air temperature.
• Take a warm shower 1–2 hours before bed. Counter-intuitively, warming up makes your body dump heat afterwards, dropping your core temperature on schedule.
• Cool your bedding. Breathable cotton or linen and a cooling mattress topper stop heat building up overnight.
• Keep your feet uncovered if you run hot — they're a major route for releasing body heat.

It works with your sleep cycles, not against them

Temperature affects how easily you move through your 90-minute sleep cycles — a hot room jolts you out of deep sleep, which is when you'd most want to stay under. Combine a cool room with well-timed sleep using the sleep cycle calculator, and cut late caffeine, which also raises your heart rate and core temperature — check yours with the half-life calculator.

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Put it into practice: pair a cool room with the right bedtime using the sleep cycle calculator.