A full-size crib is 28 inches wide and 52 3/8 inches long inside, which is 71 by 133 centimetres. That crib size is set by United States federal law, with a tolerance of 5/8 inch either way, so every full-size crib sold in the US takes every full-size crib mattress. The mattress must be at least 27 1/4 by 51 5/8 inches.
Almost nothing else in the nursery has a fixed size. Mini cribs, toddler beds, changing tables and bassinets vary by maker. Below are the official numbers where they exist, typical sizes where they do not, and how to check that everything fits your room before you order.
Crib size: the one size the law fixes
The US Consumer Product Safety Commission defines a full-size crib by its inside measurements in 16 CFR 1219: 28 ± 5/8 inches wide and 52 3/8 ± 5/8 inches long, measured between the inner surfaces of the sides and the end panels. Every full-size crib must also meet the safety standard ASTM F1169, which the same rule makes law.
The size is fixed for safety. A baby can get trapped in a gap between the mattress and the crib side, so the crib and the mattress are both made to one size and must fit each other.
| Nursery item | Inches | Centimetres | Source |
|---|---|---|---|
| Full-size crib, inside | 28 × 52 3/8 (± 5/8) | 71 × 133 (± 1.6) | 16 CFR 1219 |
| Full-size crib mattress, minimum | 27 1/4 × 51 5/8 | 69 × 131 | 16 CFR 1241 |
| Gap between crib slats, maximum | 2 3/8 | 6 | CPSC crib safety tips |
| Corner post height, maximum | 1/16 | 0.16 | CPSC crib safety tips |
| Non-full-size crib (mini crib), inside length | under 49 3/4 or over 55 | under 126.3 or over 139.7 | 16 CFR 1220 |
| Non-full-size crib (mini crib), inside width | under 25 3/8 or over 30 5/8 | under 64.3 or over 77.7 | 16 CFR 1220 |
| Toddler bed mattress, minimum | 27 1/4 × 51 5/8 | 69 × 131 | CPSC toddler bed guidance |
| European cot, inside length covered by BS EN 716 | 35.4 to 55.1 | 90 to 140 | BSI |
The CPSC says 2 3/8 inches is about the width of a soda can.
Crib dimensions on the outside: how big is a crib?
The outside crib dimensions are not fixed. The law sets the inside, and the frame, the corner posts and the headboard add to it. The plain slatted crib in the comparison further down this page measures 76 by 138 centimetres outside, about 30 by 54 inches, and a crib with thick posts or a curved headboard takes more floor.
Height is not fixed either. Check the outside width, length and height on the product page, because those are the numbers that decide if the crib fits between your window and the door.
Crib mattress size
A full-size crib mattress must measure at least 27 1/4 inches wide and 51 5/8 inches long, 690 by 1310 millimetres, under the CPSC crib mattress rule, 16 CFR 1241. Mattresses manufactured after May 3, 2026 must meet the 2025 edition of the ASTM F2933 standard, with CPSC modifications, according to the CPSC crib mattress guidance.
The two rules together leave very little room for a gap. The widest crib the law allows is 28 5/8 inches inside, and the narrowest mattress is 27 1/4 inches, so with a full-size mattress in a full-size crib, the total gap across the width is at most about 1 3/8 inches, 3.5 centimetres. The same arithmetic gives the same figure along the length. In the CPSC test, with a fitted cotton sheet on, the gap at a corner must not exceed 3.15 inches (80 millimetres).
Use a mattress sold as a full-size crib mattress in a full-size crib, and a mattress made for your exact model in a mini crib or play yard. The rule says a replacement mattress for a non-full-size crib must be at least the size of the one that came with it.
Mini crib size
A mini crib has no fixed size. The law calls it a non-full-size crib and defines it only by what it is not: an inside length under 49 3/4 inches or over 55 inches, or an inside width under 25 3/8 inches or over 30 5/8 inches, according to 16 CFR 1220. Portable cribs, crib pens and round or hexagonal specialty cribs fall under the same rule.
Because mini cribs vary, so do their mattresses. Use the mattress that came with the crib, or a replacement at least as large as that original, which is what 16 CFR 1241 requires of replacement mattresses.
Toddler bed size
A toddler bed takes the same mattress as a full-size crib, so toddler bed dimensions start from the crib mattress size. The CPSC defines it as a bed sized for a full-size crib mattress, at least 51 5/8 by 27 1/4 inches, for a child at least 15 months old who weighs no more than 50 pounds, about 23 kilograms. Toddler beds must meet ASTM F1821 under 16 CFR 1217.
That is why a crib mattress can move straight into a toddler bed, and why many cribs are sold as convertible to toddler beds with the same mattress.
Because it holds the same mattress, a toddler bed needs at least the floor space of that mattress, 27 1/4 by 51 5/8 inches, plus its frame. Check the outside size on the product page.
When to move from a crib to a toddler bed
Most children move to a bed by age 2, and one sign they are ready is reaching 35 inches tall, about 89 centimetres, according to Cedars-Sinai. The children below are shown at the same scale, from a 6-month-old baby to a 4-year-old, next to the numbers that matter for each.
-
6-month-old baby Half the crib length -
1-year-old child 74 cm (29 in) tall -
2-year-old child Near the 35 inch move-out height -
4-year-old child Toddler bed or twin bed
All four children fit the 133 centimetre crib length with room to spare, so the 35 inch sign is about height, not about the length of the mattress.
Changing table dimensions
Changing tables have no standard size. The federal rule, 16 CFR 1235, sets requirements for barriers and stability under ASTM F2388, and the CPSC defines a changing table as a freestanding structure for a child weighing up to 30 pounds (13.6 kilograms). It does not set a width, depth or height.
As one example, the IKEA SMÅGÖRA changing table is 60 centimetres wide, 81 centimetres deep and 103 centimetres high, about 23.6 by 31.9 by 40.6 inches. A changing pad on top of a dresser is an alternative, and then the dresser sets the size.
Two numbers decide if a changing table works for you:
- Height. The changing surface should be near your waist so you do not bend over for every change. Measure your own waist height and compare.
- Floor space. Compare the width and depth with the space you have, and leave room to stand in front of the table.
Bassinet dimensions
Bassinets have no fixed size either. They fall under their own federal rule, the Safety Standard for Bassinets and Cradles, 16 CFR 1218, which makes the ASTM F2194 standard law but does not set one size. Check the outside dimensions on the product page, and use the mattress or pad that came with the bassinet.
Cot size in the UK and Europe
Europe has no single fixed cot size like the US full-size crib. The British and European standard, BS EN 716-1:2017, sets safety requirements for home cots with an inside length over 900 millimetres and up to 1400 millimetres, about 35 to 55 inches.
As one example, the IKEA SUNDVIK cot takes a 60 by 120 centimetre mattress, about 23.6 by 47.2 inches, measures 125 by 67 by 85 centimetres outside, about 49 by 26 by 33 inches, and complies with EN 716-1. That is smaller than a US full-size crib, so a US crib mattress will not fit a 60 by 120 cot, and a European cot mattress is too small for a US crib. Always buy the mattress size printed on the cot.
What fits in a small nursery
The crib and the changing table above together need about 30 by 54 inches plus 24 by 32 inches of floor, before you add a chair, a dresser or space to walk. With the crib’s long side and the table side by side against one wall, that is about 78 inches of wall, or 198 centimetres.
Here is a full-size crib seen from above, 76 by 138 centimetres outside, next to children and adults at the same scale.
Before you order, mark the outside of the crib and the changing table on your floor with masking tape, as the dog crate size chart suggests for a dog’s crate. Then check three things:
- The door. Open the nursery door fully. It should not hit the crib or the table.
- The drawers. Open every drawer of the dresser or changing table. They need room in front of them.
- Your route at night. Walk from the door to the crib. If you have to turn sideways, the room is too full.
For shops that sell cribs and nursery furniture
Nursery furniture is bought before the room is finished, and the crib, the mattress and the room all have to agree. A product page that says “54 inches” leaves the parent to picture 54 inches in a room they are still painting.
Shops that sell baby products and children’s tableware use our size comparison for the same reason: shoppers want to see the product next to something they know. A crib shown next to a 2-year-old, or a changing table next to an adult, answers the question in one look.
Put the comparison next to the product photos, not on a separate size guide page that most shoppers never open. For what a size surprise costs a shop, see how to reduce returns in ecommerce.
EasySizes adds the size comparison above to a product page.
Crib size questions
How big is a crib?
A full-size crib is 28 by 52 3/8 inches inside, 71 by 133 centimetres, by federal law. The outside depends on the frame: the crib in the comparison on this page takes up 76 by 138 centimetres, about 30 by 54 inches, of floor. Mini cribs are smaller and have no fixed size.
What size mattress fits a standard crib?
A full-size crib mattress, at least 27 1/4 inches wide and 51 5/8 inches long. Any mattress sold as a full-size crib mattress in the US fits any full-size crib, because both sizes are set by the CPSC.
Do toddler beds use crib mattresses?
Yes. Under the CPSC definition, a toddler bed is sized for a full-size crib mattress, so the mattress from your crib moves straight into a toddler bed or a converted crib.
What are standard changing table dimensions?
There is no standard. The CPSC sets safety rules for changing tables but no size. The IKEA SMÅGÖRA, as one example, is 60 centimetres wide, 81 deep and 103 high, about 24 by 32 by 41 inches. Check the product page of the table you are considering.
Is a UK cot the same size as a US crib?
Not necessarily. UK and European cots have no single fixed size. The IKEA SUNDVIK cot, for example, takes a 60 by 120 centimetre mattress (23.6 by 47.2 inches), while a US full-size crib takes a mattress at least 69 by 131 centimetres (27 1/4 by 51 5/8 inches). Cots under BS EN 716 can be up to 140 centimetres long inside, so always use the mattress size printed on the cot.
When should my child move out of the crib?
Cedars-Sinai lists reaching 35 inches (89 centimetres) tall as one sign of readiness, and says most children move to a bed by age 2.