Last updated: August 11, 2021

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A comfortable cot is all your baby needs for a peaceful night's sleep, and the mattress is the main part. How to choose a cot mattress with the ideal size and right density? We want to help you with this complete guide. Follow us until the end of this article to answer all your questions and make a safe choice for your baby!


  • The cot mattress can have different measures, because there are national and international standards for cots. It is important that the mattress fits perfectly in your baby's cot.
  • The density of the mattress varies according to the baby's weight. Until 35 kg, or from birth to three years on average, the density is the same.
  • There are mattresses with anti-dust mite treatment, an interesting option to avoid respiratory allergies.

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Buying guide: everything you need to know about cot mattress

Buying a cot mattress seems like one of those simple layette tasks. And indeed it is, provided you pay attention to a few important factors to ensure your baby's safety. Come with us to learn how to choose the right model for the cot you've chosen?

Mão acariciando cabeça de bebê em seu bercinho

The mattress needs to fit perfectly in the baby's cot. Source: Helena Lopes /

What is the difference between the mattress for a national or American cot?

The first question you should ask yourself is what the standard of your baby's cot is. This is important not to buy the mattress with wrong measurements. In Brazil, two sizes of cots are commonly used, the national and American. The difference is on account of 10 centimeters on the side, since the length is the same. These measures used relate to the inside of the cradle, ie, the space where the mattress will fit. Consequently, the centimetres of the cot should be the same as the chosen mattress. Compare:

National cot American cot
Measurements 130 cm by 60 cm 130 cm by 70 cm
Indication For all ages Especially for tight quarters For all ages
Advantages Occupies less space in the bedroom More sold and with more bedding options

The height of the mattress may vary for both patterns.

What are the risks of buying the wrong mattress for my baby's cot?

Understanding the standard of your cot and buying the mattress with the right measurements is fundamental for your baby's safety. The cot mattress should fit perfectly, without gaps on the sides that create gaps between the mattress and the cot.

These gaps are extremely dangerous. The baby can fall and get stuck in this space, seriously injuring himself or even suffocating. For the cot to be a safe place, it should have nothing but the mattress with its sheet. Cot kits, blankets and pillows are not recommended, as they may cause suffocation. The nanny should only be used under adult supervision and removed after the child has fallen asleep.

What is the ideal density of the cot mattress?

The density of a mattress is the amount of foam it has for each cubic meter. In other words, it indicates how firm the mattress is and how much weight it can support. This characteristic is classified with the letter D accompanied by a number from 18 to 45. In a D18 mattress, 18 kg of foam was used in each cubic metre. This means that the heavier the person is, the higher the density should be. Therefore, for children up to 35 kg, around the age of three, the recommended mattress for cots is the D18.
When the baby's mattress is new, it should be turned every month. In addition to changing the side, also turn the position from the foot to the head, rotating it and avoiding wear on only one side

How to clean baby's mattress?

Changing the bedding is common and should be done every three days. But how are the mattresses being cleaned in your home? When it comes to babies, this care is even more important. Whenever you change the bedding, the mattress should also be cleaned routinely. This should happen at least once a week. To do this, vacuum the entire mattress, paying extra attention to the seams. After vacuuming, use a soft brush slightly dampened with water and neutral detergent.

Let it dry naturally and only after it is very dry should the bedding be put on. Ideally, the mattress should also be placed in the sun frequently. If the problem is urine, the cleaning needs to be a little different. Remove the bedclothes quickly and apply a mixture of baking soda and water on the spot. Leave it on for a few hours and then vacuum. Following the steps already mentioned.

Bebê recém-nascido em seu berço

Cleaning the mattress should be part of the routine. Source: Alicia /

Buying criteria: What to take into account when comparing different types of cot mattress

The cot mattress is an indispensable item. And although it may seem like you can choose anyone, there are actually differences that need to be considered. In addition to all the points already mentioned throughout this guide, we have selected criteria for you to compare the best mattresses.


Nowadays, most mattresses receive a treatment to avoid respiratory allergies. The technologies used reduce dust mites, fungi and bacteria that cause these allergies. But of course, that's not a reality of every mattress, so make sure it really is anti-dust mite, anti-fungal and anti-allergy.


If you have a child, you know that an important characteristic is that it should be impermeable, to prevent pee from penetrating the inside of the mattress. There are two types of waterproof mattresses:

  1. Impermeable layer: In this model, one of the surfaces is made of an impermeable plastic. The problem with this version is that only one side of the mattress offers this protection. This hinders the rotation of the mattress, which should be done monthly.
  2. Extra Protective Cover: The mattress with an extra cover makes daily life easier. It can be easily inserted and removed on either side of the mattress, and can be washed separately, better preserving both the surface and the inner part of the mattress.


We have seen that the right size is the main criterion for choosing your baby's mattress. If you have skipped this part, we recommend you to go back and understand the risks of having a mattress smaller than your child's cot. That said, the most common sizes in Brazil are:

  • National standard: 130 x 60 cm
  • American standard: 130 x 70 cm

But be warned, if your child has a mini bed, there are other variations of measurements, such as the 150 cm long. In addition, the height of the mattress may vary between 10 and 17 cm in any standard, even if the density is 18.


Although this criterion is an aesthetic detail, it is worth warning. Some children's mattresses are very colourful and patterned. This can be only on one side, usually the impermeable layer, or even all over the mattress. This characteristic can visually disturb the decoration of the room, especially when parents opt for white sheets for the baby's cot. In this sense, white mattresses are more recommended.

Quarto de bebê be decorado no estilo escandinavo

The colored mattress may disturb the decoration of the environment. Source: Sidekix Media /


The cot mattress needs to fit perfectly in the baby's cot. This criterion is the most important to ensure the safety of your child. There should be no gaps in the sides. In addition, we saw that up to 35 kg, the recommended density is D18. Throughout this guide, we brought all the comparisons for you to choose the best model. Now share it with someone who needs this information to offer a comfortable and safe night's sleep to your baby on the way.

(Featured image source: Omurden Cengiz /