Baby Sleeping Bags: Complete UK Guide (Safe Tog Ratings & Sizes)

Loose blankets in a baby's sleep space are a suffocation risk. Baby sleeping bags (also called sleep sacks or grobags in the UK) solve this problem elegantly: they keep baby warm without any loose bedding that could cover their face.

When can babies use a sleeping bag?

Most baby sleeping bags can be used from birth, provided your baby meets the minimum weight requirement (usually around 3.5kg / 7.7lbs). Smaller bags for premature or very small newborns are also available.

The Lullaby Trust (formerly The Foundation for the Study of Infant Deaths) recommends sleeping bags as a safe alternative to blankets.

What is a tog rating?

Tog is a measure of thermal resistance — essentially how warm a material is. The higher the tog, the warmer the sleeping bag.

Choose the right tog based on the room temperature where your baby sleeps:

| Room Temperature | Recommended Tog | Baby's Clothing | |-----------------|-----------------|-----------------| | 27°C + | 0.5 tog | Nappy only | | 24–27°C | 0.5 tog | Short-sleeved bodysuit | | 21–24°C | 1.0 tog | Long-sleeved bodysuit | | 18–21°C | 2.5 tog | Long-sleeved bodysuit + sleep suit | | Under 18°C | 3.5 tog or layer | Sleep suit + 2.5 tog bag |

UK homes in winter are typically 16–20°C. Most UK parents use a 2.5 tog bag October–April and a 1.0 or 0.5 tog from May–September.

Rule of thumb: If you'd be comfortable in a vest and light duvet, your baby is probably comfortable in light clothing and a 2.5 tog bag.

Signs your baby is too warm or too cold

Too warm: Sweaty neck, damp hair, flushed cheeks, clammy chest. A baby should feel warm but not hot to the touch on the back of the neck.

Too cold: Cold chest or back (hands and feet are normally cooler — don't judge by these).

Sizes explained

Baby sleeping bags are sized differently from regular baby clothing. Common UK sizing:

• Newborn / 0–6 months: ~0–6kg
• 6–18 months: Fits approximately 6–12 month clothing sizes
• 18–36 months: Fits approximately 12–18+ month clothing

It's important not to use a bag that's too big — baby can slide down inside it. Always check the weight guide, not just the age label.

Safety checklist

Before using a sleeping bag, check:

• ✅ Baby meets the minimum weight requirement
• ✅ Bag has a fitted neck that baby can't slip through
• ✅ No hood — safe sleep guidelines advise against hoods
• ✅ Zip at the front or side (shoulder zips are handy for night changes)
• ✅ Legs are free to move (hip-healthy design)
• ✅ No loose attachment points, toggles, or buttons near the face

Popular UK brands

Grobag (GroCompany) — the original UK baby sleeping bag brand, wide range of togs and sizes, excellent safety record.

Slumbersac — good value UK brand with a wide range including extra-warm options for cold homes.

Snüz — stylish designs, well-made.

Love to Dream Swaddle UP — unusual arm-up design, popular for the swaddle-to-sleeping bag transition.

Transitioning from swaddling

If you've been swaddling, transition to a sleeping bag before your baby starts showing signs of rolling (typically 3–4 months). You can use a transitional swaddle-bag hybrid (like the Love to Dream Transition bag) to ease the change.

Do you need more than one?

Most parents find two sleeping bags ideal — one in use, one in the wash. With a newborn, you'll likely be washing bags frequently, so three isn't unreasonable.

Using TinyYears to track sleep

Once you've set up a consistent sleep environment, use TinyYears to track sleep patterns and see how changes (new bag, different tog, temperature changes) affect your baby's sleep quality.