TL;DR

• The standard crib size in Canada is an interior of roughly 71.1 cm by 132.1 cm.

• A standard crib mattress measures 69.2 cm by 131.1 cm minimum and up to 15 cm thick.

• Health Canada allows a gap of no more than 30 mm between mattress and crib sides.

• Mini crib mattresses are a different size and never interchangeable with standard ones.

The standard crib size question comes up at nearly every crib fitting Kido Bébé’s Montreal team does, and the answer is set by regulation rather than guesswork. This guide lays out the crib and mattress dimensions, the mini crib alternative, and the quick at-home check that confirms a proper fit, all tied to Health Canada’s crib safety standards →

The Standard Full-Size Crib Interior

The standard crib size in Canada, for a full-size crib built to regulation, is an interior of roughly 71.1 cm by 132.1 cm, or about 28 by 52 inches. That interior is the space the mattress needs to fill, measured from inside rail to inside rail at the level of the mattress support.

Model-to-model variation stays within a small tolerance around these numbers, which is why a properly labelled standard mattress fits a properly built standard crib without guesswork.

The Standard Crib Mattress Size

The standard crib mattress size in Canada is at least 69.2 cm by 131.1 cm, or 27.25 by 51.625 inches. Those figures are a minimum, not a maximum.

Any mattress labelled standard or full-size should meet or exceed them while still fitting inside the crib’s interior, which leaves only a narrow margin along each side. A mattress that falls short of the minimum, even by a little, is a common cause of a failed gap check.

Why Mattress Thickness Matters Too

Length and width get the attention, but thickness has its own limit. A standard crib mattress must not exceed 15 cm, or 6 inches, in thickness.

A thicker mattress raises the sleep surface closer to the top rail, which reduces the effective rail height once a baby starts to push up or pull to stand. The crib’s height settings are designed around a mattress within that limit, so a thicker one undoes part of the safety margin built in.

The 30 mm Gap Rule

Health Canada’s regulation sets a clear fit rule: when the mattress is pushed to one side of the crib, the gap on the opposite side must not exceed 30 mm, roughly the width of two adult fingers.

The limit exists because a wider gap is an entrapment hazard. An infant can wedge a face, arm, or leg between the mattress and the crib side. The rule applies at every mattress height setting, not only the highest.

How to Check Your Mattress Fit at Home

The two-finger test takes a moment and needs no tools:

1. Push the mattress firmly against one side of the crib.

2. Try to slide two fingers into the gap on the opposite side.

3. If two fingers fit easily with room to spare, the gap is too wide and the mattress is too small for that crib.

A mattress that fails the test should be replaced, not padded out with towels or foam.

Mini Cribs: A Different Set of Dimensions

Mini cribs are a different category, not a smaller standard crib. A mini crib mattress measures around 61 cm by 96.5 cm, or 24 by 38 inches, which makes it shorter and narrower than a standard mattress.

The two sizes do not mix: a mini crib mattress leaves dangerous gaps in a standard crib, and a standard mattress will not fit a mini crib. If space is tight, browse Kido Bébé’s mini crib collection and match the mattress to it.

Measuring Your Own Crib Correctly

If you are buying a mattress separately, measure the crib rather than trusting the box. Measure the interior at the level of the mattress support, not at the top of the rails, since rails can read wider at the top.

Take the width from side to side and the length from end to end, then compare both numbers against the standard crib dimensions above before choosing a mattress. Write the numbers down and bring them shopping.

Shop at Kido Bébé Montreal

Confirming crib size in Canada is easiest when the crib and mattress are in the same room. At Kido Bébé’s showroom, 4100 Boulevard Thimens in Saint-Laurent, the in-store team can check a crib and mattress together before purchase. Every crib in Kido Bébé’s crib collection is offered to meet Health Canada’s SOR/2016-152, and as an authorized retailer we can pair each one with a correctly sized mattress. Drop in, or browse the collection online.

Buying the Crib and Mattress Together vs Separately

Both routes are safe when the numbers are confirmed:

Buying separately works as long as the mattress meets the minimum size, stays under the thickness limit, and passes the two-finger test.

Why These Numbers Are Regulated, Not Arbitrary

Health Canada’s Cribs, Cradles and Bassinets Regulations, SOR/2016-152, set these dimensions for one reason: preventing entrapment and suffocation hazards. Standardized crib dimensions mean any properly labelled standard mattress fits any properly built standard crib, so a parent does not have to engineer the fit themselves.

That consistency is a safety feature, not a manufacturing convenience. Every number in this guide, from the interior measurement to the 30 mm gap, exists because a mismatch between mattress and crib has consequences.

Secondhand Cribs and Mattress Fit

A crib passed down from a relative or bought secondhand may have interior dimensions that predate what current mattresses are sized for. Never assume it matches the standard crib size.

Measure the interior at the mattress support, compare the numbers against the figures above, and run the two-finger gap check with the actual mattress you plan to use. If the gap fails, the fix is a correctly sized mattress or a different crib, never a folded blanket in the gap.

Getting the Fit Right From the Start

Knowing the standard crib size and matching it to a properly sized mattress is one of the simplest ways to build a safe sleep space. The numbers are set by regulation for a reason, and a quick two-finger check at home confirms the fit before a baby ever sleeps in the crib. Ready to set up the nursery? Come see the cribs at Kido Bébé in Saint-Laurent, or shop cribs and mattresses online.