Quick answer
Buy the size that matches your cot or cot bed's internal base dimensions: 60x120cm for a standard cot, 140x70cm for a standard cot bed. Measure the internal length and width with a tape before ordering, because a sprung mattress must sit flush with no gaps at the edges.
Why the two sizes are not interchangeable
A 60x120cm mattress is sized for a cot, which typically has higher sides and a smaller sleeping area. A 140x70cm mattress is sized for a cot bed, which is longer and wider and often converts to a toddler bed later. The difference is not cosmetic: a mattress that is too short or too narrow leaves gaps where a baby can become wedged, and one that is too large will not sit flat on the base.
Sprung mattresses add a further constraint. The spring unit and foam support walls need to rest evenly on the cot base, so the mattress must match the internal dimensions closely. If your cot has a non-standard base or rounded corners, check the manufacturer's stated mattress size rather than assuming either of these two sizes will fit.
Pocket springs vs open springs in a cot mattress
Pocket sprung mattresses use individually pocketed springs, so each spring responds to pressure on its own. In a cot mattress this can help spread support across the sleeping surface rather than concentrating it. Open sprung mattresses use linked springs, which are usually firmer and less contouring. Neither is automatically better for every baby; the choice depends on how much contouring support you want and how the mattress is constructed overall.
Firmness matters more than spring count for newborns. A sprung mattress should still feel firm and flat, with no soft dips. If you can press the surface down easily or feel the springs through the padding, it is not suitable for a baby.
When a 140x70cm cot bed mattress is the wrong choice
A 140x70cm mattress will not fit a standard 60x120cm cot, and folding or squeezing it into a smaller frame creates gaps and uneven support. Likewise, a 60x120cm mattress in a cot bed leaves a large gap at the foot or side. If you are buying for a cot that later converts to a cot bed, check whether the conversion requires a different mattress size; many cot beds use the 140x70cm size from the start, but not all do.
If you are unsure which size you need, measure the internal base of your cot or cot bed, not the outer frame. The internal measurement is the one that determines mattress fit.
Decision rules for choosing your sprung cot mattress size
- Measure the internal base: Use a tape measure to record the internal length and width of your cot or cot bed base. Compare the result to 120cm x 60cm or 140cm x 70cm. If your measurement is within about 1cm of one of these, that is your size. Write the measurement down and take it with you when shopping.
- Check for gaps at the edges: After fitting, press the mattress into each corner and run your fingers around the edge. A correct fit leaves no gap wider than about two fingers. If you can fit more, the mattress is too small. Test the fit before removing any packaging or using the mattress.
- Match the mattress to the cot type, not the child's age: A cot uses a 60x120cm mattress; a cot bed uses a 140x70cm mattress. Do not size up early or fold a larger mattress to fit a smaller frame. If your cot converts to a cot bed, confirm the required mattress size in the cot's instructions.
Product facts
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Tutti Bambini Pocket Sprung Cot Mattress 60x120cm: Individually pocketed spring system with high-density foam support walls and a removable, washable cover. The pocket springs and foam walls are designed to give balanced support, and the washable cover makes it easier to keep the sleeping surface clean.
Tutti Bambini Pocket Sprung Cot Mattress 60x120cm
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CuddleCo Mother&Baby Pure Gold Anti-Allergy Coir Pocket Sprung Cot bed Mattress 140 x 70cm: Pocket sprung support with a natural coconut coir layer, TENCEL fibres, and Purotex anti-allergy technology. The coir layer adds a breathable natural component, while the anti-allergy treatment is aimed at reducing allergens in the sleep environment.
CuddleCo Mother&Baby Pure Gold Anti-Allergy Coir Pocket Sprung Cot bed Mattress 140 x 70cm
Who each size suits
Best for
- Parents with a standard 60x120cm cot who want a pocket sprung mattress with a washable cover
- Parents with a 140x70cm cot bed who want a pocket sprung mattress with a natural coir layer and anti-allergy treatment
Not for
- Cots or cot beds with non-standard internal dimensions; measure first and choose a custom-fit mattress
- Anyone who has not measured the internal base, since either size will be unsafe if it does not fit flush
