When should a child move to a Single mattress?

When height, climbing behaviour and carer judgement say the cot or Small Single is outgrown. There is no single age. Safety and rail rules on bunks still apply.

Can adults use a kids mattress?

Size may fit a Single frame, but construction and weight limits may be lighter. Check stated limits on the label.

How thick can a bunk mattress be?

Only as thick as the bunk maker allows so guardrails stay high enough. Measure the rail and read the frame instructions before buying a deep adult-style mattress.

sizing

Kids Mattress Guide (Cot to Single)

Entity: kids mattress guide

Bright children’s bedroom with a neat single bed and soft bedding — Kids’ sizes step up from cot bed to Small Single and Single — always check the frame rules.

In short

Children's mattresses go from cot bed (~70 × 140 cm) to Small Single (75 × 190 cm) and Single (90 × 190 cm). Cot mattresses must fit the cot snugly for safety. Kids' beds and bunks often limit mattress depth for guardrails. Support growing bodies without adult marketing extremes — follow cot and bunk depth and safety rules first.

Educational progression diagram from cot bed to Small Single to Single mattress footprints — Size up by centimetres and cot/bunk rules — not by adult Double or King names.

Dimensions (centimetres and inches)
Size name	Width (cm)	Length (cm)	Width (in)	Length (in)
Cot bed	70	140	—	—
Small Single	75	190	—	—
Single	90	190	—	—

Size ladder

Children usually move through stages. Exact centimetres beat age myths.

Stage	Typical size idea	First check
Cot / cot bed	Model-specific (often ~60×120 or ~70×140 cm bands)	Snug fit — no gaps
Small Single	75 × 190 cm	Room and bed type
UK Single	90 × 190 cm	Standard next step for many older children

Details: cot and Small Single and the full kids size journey.

Safety rules that outrank marketing

Infant safer-sleep guidance comes from health authorities — not mattress ads
Cot fit must be snug to the manufacturer’s size
Bunk / high sleeper age, weight and guardrail rules are mandatory reading — bunks
Mattress depth on bunks protects rail height

Compare layouts: bunk vs high sleeper.

Firmness without adult slogans

Growing bodies need a supportive, even surface. Extreme “hotel soft” pillow-tops are rarely the first kids need. Adult soft/medium/firm labels still mix support and quilt — teach the difference early.

Common mistakes

Buying a deep adult mattress for a bunk that only allows a thin one
Assuming every “cot bed” mattress is interchangeable
Skipping the assembly and rail checks

Frequently asked questions

When should a child move to a Single mattress?: When height, climbing behaviour and carer judgement say the cot or Small Single is outgrown. There is no single age. Safety and rail rules on bunks still apply.
Can adults use a kids mattress?: Size may fit a Single frame, but construction and weight limits may be lighter. Check stated limits on the label.
How thick can a bunk mattress be?: Only as thick as the bunk maker allows so guardrails stay high enough. Measure the rail and read the frame instructions before buying a deep adult-style mattress.