What size is a cot mattress?
Short answer: Standard cot mattresses are commonly 120 x 60cm, and space-saver cots often take 100 x 50cm. Check your cot's internal size.
Here is the detail behind that answer, taken from current UK guidance from the NHS and the Lullaby Trust.
Things to check
- Measure the inside of the cot. The mattress should fit with no gaps.
- Choose firm, flat and waterproof. Your baby's head should sink no more than a few millimetres.
- Check for a fire-resistant label and the relevant British Standard.
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 mattress?
A firm, flat mattress for a standard cot, usually 120 x 60cm.
Shop at Baby Kingdom
Browse cot mattresses 120 x 60
- Obaby Pocket Sprung Mattress - 120 x 60cm
- Obaby Sprung Mattress - 120 x 60cm
- Obaby Eco Foam Cot Mattress 120 x 60 cm
- Obaby Moisture Management Mattress -120x60cm
Check each product page for its exact dimensions, mattress size, age and weight limits and safety standards.
More advice
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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.