Do I need a 3.5 tog baby sleeping bag in the UK?

What togs does the NHS actually list?

On NHS safer sleep the commercial sleeping-bag list is only:

• 2.5 tog for all year and standard rooms of 16 to 20C
• 1.0 tog for warmer weather and rooms of 20 to 24C
• 0.5 tog for hot weather and rooms of 24 to 27C

There is no 3.5 line on that page. There is also no NHS sentence that says a UK winter requires 3.5. The first-year buy list therefore treats 2.5 as the cold-end official bag, not 3.5.

Lullaby Trust: aim for a 16–20°C sleep room, check the chest or neck, and if you use a sleeping bag do not add extra blankets on top — add a clothing layer or choose a higher tog if baby feels cold. The Trust does not publish a 3.5 rule.

What do brands mean when they sell 3.5 as 'winter'?

Shop charts often print 3.5 for rooms below 16°C. Love to Dream's UK tog article and its 3.5 sleep-bag listing say 3.5 TOG <16°C, with one long-sleeve merino-mix bag priced at £54.99 on 10 September 2026. Some supermarket hangtags use a similar below-16°C line. That is the maker's temperature column, not a missing NHS band.

Should I buy 3.5 for a cold unused room?

Parent threads split because some UK bedrooms drop below 16°C when the heating is off. That is a room problem first. Lullaby Trust says it can be tempting to wrap baby up when it is cooler than 16°C, and still warns that overheating raises SIDS risk. Its dressing page tells you not to add blankets on a bag, and to add a clothing layer or a higher tog if the chest feels cold.

1. 1
   Measure the room at 2am, not the weather app Put a room thermometer in the sleep space. If nights sit at 16–20°C, the NHS bag is 2.5. A 3.5 is a skip.
2. 2
   Warm or close the unused room A loft bedroom that is 12°C because the radiator is off is cheaper to heat a few degrees than to kit out with a fourth tog you only use on those nights.
3. 3
   Try a clothing layer under the 2.5 That is the Lullaby Trust order: layer of clothes, or a higher tog if baby feels cold. It is not permission to pile blankets on the bag.
4. 4
   Only then look at a 3.5 SKU If the thermometer still sits below the temperature printed on that maker's 3.5 chart, the bag is a narrow extra — one unit, not a first-year set. Keep a 2.5 for nights the room is back in band.

When is 3.5 a skip, and when is it a wait?

• Skip now if you have not measured the room, or the room already sits at 16–20°C. The first-year list does not include 3.5.
• Wait if you are buying before birth and do not know whether the baby will sleep in a heated parents' room (NHS: same room for the first six months) or a cold spare.
• One bag later only if repeated night readings stay below the maker's own 3.5 line and you have already tried heating and a clothing layer under 2.5.

A 3.5 does not replace the wash spare. You still want two bags of the tog you use most. Do not wear 3.5 plus 2.5 together.

In shortIn short: NHS does not list 3.5. Brands sell it for rooms they call below about 16°C. That is not an official winter rule. Skip it for a normal 16–20°C room; wait until a thermometer — not the word 'winter' on the box — creates the gap.