Which TOG rating suits which room temperature?

0.5 TOG from about 24 °C, 1.0 TOG at 20–23 °C, 2.5 TOG at 16–20 °C and 3.5 TOG below 16 °C. The ideal sleep temperature is 16–20 °C.

What should the baby wear under the sleep sack?

Depending on the room temperature: above 24 °C just a diaper or short-sleeve bodysuit, at 20–23 °C a bodysuit, at 16–20 °C a long-sleeve bodysuit (plus romper at 16–18 °C) and below 16 °C a long-sleeve bodysuit with a warm sleepsuit.

What if I don't have a sleep sack?

A sleep sack is safest because loose blankets don't belong in the crib. Without a sleep sack, a well-fitting sleepsuit of the right warmth helps; avoid pillows, loose blankets and a hat in bed.

← What should my baby wear?

Dressing your baby at night

At night, safe sleep comes first: a baby sleep sack instead of loose blankets, a rather cool room temperature and no overheating. How warm the sleep sack should be is told by its TOG rating – matched to the temperature in the bedroom.

In short: ideal sleep temperature 16–20 °C. Choose the sleep sack by TOG, underneath a bodysuit or sleepsuit – no hat, no loose blankets. Check for overheating at the chest/neck.

TOG chart: sleep sack & what goes underneath

Room temperature	TOG rating	Under the sleep sack
from 24 °C	0.5 TOG (summer)	Diaper only or a short-sleeve bodysuit
20–23 °C	1.0 TOG (spring/autumn)	Short- or long-sleeve bodysuit
16–20 °C	2.5 TOG (all year)	Long-sleeve bodysuit (+ romper at ~16–18 °C)
below 16 °C	3.5 TOG (winter)	Long-sleeve bodysuit + warm sleepsuit

The sleep sack calculator shows you the right value directly for your room temperature.

Safe sleep

💤 Ideal sleep temperature 16–20 °C. Babies are safer slightly too cool than too warm. No hat in bed, no loose blankets or pillows, a sleep sack in the right size (the baby must not be able to slip down inside it). Check for overheating at the chest or neck – not at hands or feet.

When it gets cooler at night

If the temperature drops below 18 °C you have two options: choose a warmer sleep sack (2.5 instead of 1.0 TOG) or put a long-sleeve bodysuit on under the 2.5 TOG sack. Both together only when it's really cold – and then check the neck in the morning.

🌙 Open the sleep sack calculator

Frequently asked questions

Which TOG rating at which temperature?

0.5 from 24 °C, 1.0 at 20–23 °C, 2.5 at 16–20 °C, 3.5 below 16 °C. Ideal 16–20 °C.

What goes under the sleep sack?

Depending on the temperature, from diaper/bodysuit to long-sleeve bodysuit + sleepsuit (see chart).

And without a sleep sack?

A sleep sack is safest. Otherwise a well-fitting sleepsuit, no loose blankets, no pillow, no hat.

By Felix & Merle · parents of Josefine

We built HeyFini out of our own everyday life with a baby. Our recommendations are based on recognised sources (among them the Lullaby Trust for safe sleep and the ADAC, Germany's automobile club, for car-seat safety) and our own experience as parents – more in our story. Last updated: June 2026.

More dressing guides

General guidance, not medical advice. When in doubt, ask your paediatrician or midwife.