Which mattress fits in a crib for your baby?
The question of which mattress fits a cot seems simple until you are faced with different sizes, materials, and thicknesses. Yet safe baby sleep does not start with the prettiest cover or the softest feel, but with a mattress that fits the bed exactly and provides proper support for your baby. With the right choice, you create a calm, well-maintained sleeping space where comfort and safety come together naturally.
Which mattress fits a cot?
A cot mattress must primarily match the internal dimensions of the cot exactly. The two most common sizes are 60 x 120 cm and 70 x 140 cm. Always measure the inside of the bed, especially if you are using a vintage cot, choosing a model from a different brand, or using a bed handed down from family.
The mattress should lie flat on the bed base, without raised edges, folds, or gaps on the sides. No opening should be created where your baby could get a hand, foot, or head stuck. Always consult the cot's user manual as well: some models have a recommended mattress height or maximum thickness, ensuring the height of the bed rail remains safe as your child grows.
A 60 x 120 cm mattress should therefore only be used in a cot with the same internal dimensions. "Padding out" a smaller mattress with pillows, muslin cloths, or rolled-up blankets is not a safe solution. If the size is not exactly right, it is better to choose a new mattress that fits well.
Cots, cribs, and toddler beds are not the same
A crib mattress is smaller and often thinner than a cot mattress. Therefore, do not use a crib mattress in a cot, even temporarily. The same applies in reverse: a cot mattress is too big for a crib and can buckle or get jammed.
With a 70 x 140 cm convertible bed, you can sometimes create a smaller sleeping area first using a special, matching system from the manufacturer. Always follow the instructions that come with the bed. As soon as your child is ready for the full length, a matching 70 x 140 cm mattress is the logical choice.
Choose firm, even support
For adults, a soft mattress often feels comfortable. It works differently for babies. A baby benefits from a flat and firm sleeping surface that supports the body evenly. The mattress may yield slightly under pressure, but your baby should not sink deep into it.
Press your hand into the mattress and see how quickly the material springs back. A quality mattress quickly regains its shape and remains even even with daily use. Pay close attention to sagging: a mattress with a permanent indentation offers less effective support and is due for replacement.
The right firmness is not a matter of choosing the hardest mattress. A very hard board without resilience is just as unpleasant. Look for the calm middle ground: stable, flat, dimensionally stable, and comfortable enough to support a relaxed sleeping position.
How thick should a cot mattress be?
The ideal thickness depends on the cot's design and the manufacturer's instructions. Many cot mattresses are about 8 to 12 cm thick. Thicker is not automatically better. A mattress that is too high can lower the protective bed rail, especially once your baby starts pulling themselves up.
After placing the mattress, always check the distance between the sleeping surface and the top of the bed rail. This distance must remain sufficient for your child's developmental stage. Lower the base of an adjustable cot in time when your baby starts rolling, sitting, or standing.
Material: ventilation, hygiene, and daily convenience
The material partly determines how well a mattress ventilates, retains its shape, and can be kept clean. Cold foam is popular because it can be lightweight, resilient, and well-ventilating. Polyether foam is often an accessible choice, but the quality can vary per version. Latex has a resilient character but is generally heavier. There are also mattresses with a core of natural fibers or materials chosen with sustainability in mind.
There is no single material that is best for every family. In a warm bedroom, ventilation might be an extra important factor. If you have a baby who spits up regularly or has problems with leaking diapers, a well-removable, washable cover is particularly practical. When choosing, look not only at the core but at the entire mattress: the ticking, zipper, finishing, and washing instructions make a big difference in daily life.
A breathable mattress protector helps keep the mattress fresh for longer. Choose a protector that fits well and stays tight around the mattress. A thick, loose topper or extra soft mattress pad does not belong in a baby cot. It alters the flat sleeping surface and can shift.
Pay attention to quality marks and clear product information
A carefully chosen cot mattress provides clarity about size, composition, maintenance instructions, and safety standards. The European standard EN 16890 is specifically relevant for mattresses for children's beds. Also, check whether a product is free of unwanted substances and whether the materials are suitable for intensive use in a nursery.
Quality marks can help with your choice, but they never tell the whole story. Also look at the finishing: a solid zipper, a cover that you can actually wash, and a core that retains its shape say a lot about longevity. For a nursery that has been furnished with care, a durable mattress is a quiet but valuable foundation.
Make the bed up deliberately simply
A matching mattress is the start. For babies, a calm, empty sleeping environment remains the starting point. Use a well-fitting fitted sheet and, depending on age and season, for example, a sleeping bag that suits your child. Loose pillows, thick duvets, soft toys, sleep nests, and positioning cushions do not belong in the cot while sleeping.
That does not mean the nursery has to feel austere. Precisely by choosing refined colors, soft lighting, beautiful storage, and carefully selected materials around the bed, a calm atmosphere is created. You keep the sleeping surface itself safe and uncluttered, so your child has plenty of room to rest undisturbed.
Wash fitted sheets regularly and let the mattress air out occasionally by leaving the bed open for a while. Only rotate or turn the mattress if the manufacturer recommends it. Some mattresses have a clear summer and winter side, while others are intended to be used on the same side at all times.
When should you replace a cot mattress?
A mattress does not automatically go to the next child. Replace it when you see sagging, tears, moisture stains, a musty odor, or damage to the cover. Even if the mattress no longer lies perfectly flat or has become noticeably softer, a new one is wise.
When reusing, a critical judgment is extra important. A mattress that has always been kept dry, well-protected, and is still completely dimensionally stable can sometimes still be perfectly fine. But when in doubt, it is better to choose certainty. A new, carefully selected mattress provides not only a fresh start but also the peace of mind that the size, support, and hygiene are correct again.
At PetitDame, a beautiful nursery is therefore never just about what you see. The most beloved spot in the room begins with what you barely notice: a safe, fitting, and comfortable mattress on which your baby can sleep securely every night.
