Optimal Sleep Temperature Calculator

Your core temperature falls by about 1 degree Celsius through the night, and the fall starts in the evening, before you are asleep. That is why a room that is too warm makes falling asleep difficult: your body cannot shed heat fast enough to make the drop happen.

The ideal bedroom temperature range

The figure you will see everywhere, 15.5-19.4C (60-67F), is the Sleep Foundation’s advice and what most sleep doctors repeat, rather than the result of one trial. It assumes ordinary bedding. Within it, most adults can lose heat comfortably as they fall asleep and stay asleep through the night.

Measured sleep points a little warmer for older people. In a 2023 study that tracked 50 adults over 60 for close to 11,000 nights (Baniassadi and colleagues), sleep was most efficient with the bedroom at 20-25C (68-77F), and efficiency fell by 5 to 10% as the room went from 25 to 30C. That is why this calculator starts an older person higher. Children also tend to sleep better toward the warmer end. Menopausal women often need the cooler end or beyond, and vasomotor symptoms respond to room temperature more than almost anything else you can change without a prescription. This calculator has no input for that, so if night sweats are the problem, start at the cool end of your range and work down rather than treating the number below as a target. Heavy people run warmer than thin people and generally prefer cooler rooms.

Infants are a different question entirely. Safe-sleep guidance for babies runs roughly 16-20C (61-68F), and overheating is an established SIDS risk factor, so this is one case where you should follow paediatric guidance rather than a general calculator. That is why the age field here starts at 5.

What happens when the room is too warm

Above about 24-25C (75-77F), sleep efficiency drops measurably. REM tends to go first, because the body all but switches off its temperature control during REM, so in a hot room it avoids entering that stage. Hot nights systematically shorten REM, which shows up the next day as worse memory consolidation and shorter emotional fuses.

Core temperature manipulation

A warm shower or bath 1-2 hours before bed counterintuitively improves sleep by triggering vasodilation in the hands and feet, dumping heat from the body’s core. A 2019 review of 17 studies (Haghayegh and colleagues) found that water at 40-42.5C (104-109F), even for 10 minutes, helped people fall asleep faster, by about 10 minutes on average. Wearing socks to bed works the same way: warming the extremities pushes heat out of the core.

In summer, a box fan drawing cool night air is often more effective than air conditioning set too cold, because airflow improves evaporative cooling from the skin surface.