What size is a cot bed mattress?
Short answer: Cot bed mattresses are commonly 140 x 70cm, but always check the exact size for your frame, because the mattress must fit with no gaps.
Here is the detail behind that answer, taken from current UK guidance from the NHS and the Lullaby Trust.
Things to check
- Confirm the cot bed's mattress size before buying, as frames vary.
- Firm, flat, waterproof, with a snug fit.
- Choose foam, spring or fibre for your budget and how much you need to wipe or wash it.
What the guidance says
- Use a firm, flat, waterproof mattress in good condition, with no raised or cushioned edges, that fits the cot or Moses basket with no gaps.
Related questions
What is a cot bed mattress?
A firm, flat mattress for a cot bed, usually 140 x 70cm, which carries on into the toddler-bed stage.
Shop at Baby Kingdom
- Tutti Bambini Eco Fibre Cot Bed Mattress (70 x 140 cm)
- Kidsaw Pocket Sprung Toddler Mattress 70 x 140cm
- Tutti Bambini Natural Coir Fibre Cot Bed Mattress (70 x 140 cm)
- Ickle Bubba Premium Sprung Cot Mattress 140 x 70cm
Check each product page for its exact dimensions, mattress size, age and weight limits and safety standards.
More advice
Are all cot mattresses the same size?Should a cot mattress be firm or soft?Baby mattress sizes explainedCan I use a second-hand cot mattress?Is a Moses basket mattress right for you? Quick quizWhich baby mattress size do you need?All cot and baby mattresses advice →
Sources
- The Lullaby Trust: Baby mattresses and bedding (accessed 2026-10-21)
General information only, not medical advice. Always follow your product's instructions. If you are worried about your baby, contact your GP, health visitor or 111. In an emergency, call 999.