What's the Best Room Temperature for a Sleeping Baby?
UK safe-sleep bodies (The Lullaby Trust, NHS) recommend a room of about 16-20°C (61-68°F). Slightly warmer is workable if you dress your baby lighter. The principle behind every number: a comfortably cool room beats a warm one, because overheating is the documented risk.
New parents fixate on this number, and it's easy to see why: it feels like the one thing you can measure. But the range exists to serve a simpler idea. Your baby doesn't need a perfect thermostat - they need the right outfit for whatever the room actually is.
Where 16-20°C comes from
The Lullaby Trust and the NHS both name 16-20°C as the comfortable, safer range for infant sleep, tied to decades of research linking overheating to sudden infant death syndrome (SIDS). The American Academy of Pediatrics phrases it functionally rather than numerically: avoid overheating and overbundling, and dress infants appropriately for the environment with no more layers than an adult would be comfortable in.
To most adults, 16-20°C reads as slightly cool. That's the point. Babies handle a comfortably cool room dressed correctly far better than a warm one.
When your nursery won't cooperate
Top-floor flat in July, old radiators you don't control, a heatwave. You often can't move the number - so move the layers instead:
| The room is… | Reach for… |
|---|---|
| Below 16°C | Higher-TOG sack (2.5) + sleepsuit + bodysuit - not extra room heating overnight |
| 16-20°C | The classic setups: 1.0-2.5 TOG depending on where in the range you are |
| 21-24°C | Lighter sack (1.0 → 0.5 TOG), short sleeves underneath |
| Above 24°C | 0.5 TOG or just a bodysuit; a room fan (not aimed at baby) helps air move |
The full outfit-by-temperature chart lives in our guide to what your baby should wear to sleep.
Measure where it matters
Hallway thermostats routinely disagree with the crib corner by two or three degrees. Put a small thermometer near the crib at mattress height, away from radiators, vents, and windows. That's the number your baby sleeps in - and the one worth acting on.
The check that beats every number
Whatever the thermometer says, your baby's chest settles the question. Ten to fifteen minutes after settling, feel the chest or back of the neck: warm and dry means right; sweaty means remove a layer; cool means add one. Cool hands and feet alone are normal and not a signal - more on that in how to tell if your baby is too hot or too cold.
TinyLayers does this arithmetic for you.
Enter tonight's room temperature and get the exact sack and layer - tuned to your baby's age and how they run. Learn more →
Sources
TinyLayers provides general dressing guidance only and does not replace medical advice. Every baby is different - for fever, premature birth, or any medical concern, follow your clinician's guidance.