Sleep-Sack TOG Calculator
Match the sleep-sack warmth to the room. Enter the nursery temperature for the right TOG and the light layers to wear underneath.
Warmth you can trust, without loose bedding
A sleep sack is popular because it keeps a baby warm at a known, rated level and can’t be kicked off to cover the face the way a blanket can. The trick is matching the TOG to the room and keeping the under-layers light, so the total warmth stays in the comfortable band through the night even as the room cools toward morning.
Set the room itself with the Baby Room Temperature & TOG Guide, and dress baby for daytime cold with the Baby Layering Guide.
Frequently Asked Questions
What TOG sleep sack should my baby wear?
It depends on the room temperature. Warm rooms need a low-TOG sack and cool rooms a higher one: broadly, a 0.5 TOG sack above about 24°C, a 1.0 TOG sack around 21–23°C, a 2.5 TOG sack from roughly 16–20°C, and a 3.5 TOG sack below 16°C. This calculator takes your measured room temperature and returns the matching TOG plus the under-layers to pair with it.
What should my baby wear under a sleep sack?
The sack provides the main warmth, so the layers underneath are light and set by the room: a nappy only in a hot room above about 27°C, a short-sleeve bodysuit in a warm room, a long-sleeve bodysuit in a mild one, and a bodysuit with a sleepsuit in a cool room. The tool lists the recommended combination for the temperature you enter so you don't over- or under-dress under the sack.
What if the room is colder than 16°C?
The safer fix is to warm the room toward the recommended 16–20°C range rather than piling on extra layers, because loose layers and blankets raise the risk of overheating and of covering the face. If the room can't be warmed, a higher-TOG sack with an appropriate under-layer is better than adding a blanket. The tool flags a below-range room when you enter one.
Is this medical advice?
No. This is general, informational guidance based on the widely-used sleep-bag TOG charts and the room temperature you enter — not medical advice. Sacks vary by brand, so check the label, judge warmth by feeling the back of the neck or chest, and follow current safe-sleep guidance from your pediatrician or health service.
Informational only, based on common sleep-bag TOG charts and the temperature you enter — not medical advice. Follow your sack’s label and current safe-sleep guidance, and consult your pediatrician with any concern.