Kids Mattress Guide (Cot to Single)
Published 2026-08-03. Last updated 2026-08-03. Desk research by Kaiser Khan — we have not product-tested kids mattress guide. This is not a shop review and not medical advice.
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.
About 2 minutes to read
| 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
Related BedGuide entries
How it works
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.