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Cot Bed and Small Single Mattress Sizes

Entity: cot bed and small single mattress sizes

Children’s bedroom with a small neat bed
Cot and Small Single sizes are smaller than a full UK Single.

In short

A common UK cot bed mattress measures about 70 × 140 cm and must fit the cot snugly for infant safety. A UK Small Single is typically 75 × 190 cm — narrower than a standard Single at 90 × 190 cm — used for children, compact rooms and some bunks. Confirm exact manufacturer dimensions before ordering sheets or frames.

How it works

Size ladder diagram from cot mattress to Small Single and UK Single in centimetres
Children’s sizes step up by centimetres. Cot fit must be snug to the cot model.
Dimensions (centimetres and inches)
Size name Width (cm) Length (cm) Width (in) Length (in)
Cot bed (common UK) 70 140 27.6 55.1
Small Single 75 190 29.5 74.8
Single (reference) 90 190 35.4 74.8

Cot fit is a safety size problem

Unlike adult approximate sizes, cot mattresses must match the cot’s internal space. A mattress that is too small creates dangerous gaps. One that is too large will not sit flat. Use the cot maker’s stated centimetres.

Progression through UK children’s sizes

  1. Cot bed — ~70 × 140 cm (verify per cot).
  2. Small Single — 75 × 190 cm.
  3. Single — 90 × 190 cm (standard adult/guest Single).

Adult couples’ sizes begin at Small Double / Double.

Frequently asked questions

What size is a UK cot bed mattress?
Many UK cot bed mattresses are approximately 70 cm by 140 cm. The critical rule is a snug fit in the specific cot with gaps small enough that a child cannot become trapped — follow the cot manufacturer's stated mattress size.
When do children move from cot to Small Single or Single?
Timing depends on height, climbing behaviour and safety guidance from carers. Dimensionally, Small Single (75×190 cm) and Single (90×190 cm) are the common next UK footprints.