Crib Sizes: Standard, Mini and International Crib Dimensions
For parents planning a nursery or buying a mattress and sheets. US full-size cribs are one of the few pieces of furniture whose inside dimensions are set by federal law, so the numbers below are fixed rather than typical.
A standard (full-size) US crib has an interior of 28 × 52⅜ in (71 × 133 cm), give or take ⅝ in, and takes a 28 × 52 in (71 × 132 cm) crib mattress no more than 6 in (15 cm) thick. The outside of the crib usually measures about 29-31 × 53-57 in (74-79 × 135-145 cm). Mini cribs typically use a 24 × 38 in (61 × 97 cm) mattress.
- Crib interior
- 28 × 52⅜ in
- Standard mattress
- 28 × 52 in
- Max mattress depth
- 6 in (15 cm)
- Max slat gap
- 2⅜ in (6 cm)
On this page
Standard crib size: what the federal rule fixes
In the US, a "full-size crib" is defined by its inside measurements. Anything outside the tolerances below is legally a non-full-size crib, which falls under a different standard and uses a different mattress.
| Measurement | Inches | Centimeters | Rule |
|---|---|---|---|
| Interior width | 28 ± ⅝ | 71 ± 1.6 | Measured between the inside faces of the sides |
| Interior length | 52⅜ ± ⅝ | 133 ± 1.6 | Measured between the inside faces of the ends |
| Mattress, minimum size | 27¼ × 51⅝ | 69 × 131 | 16 CFR 1241 |
| Mattress, maximum thickness | 6 | 15 | Thicker mattresses cut the usable rail height |
| Gap between slats | 2⅜ max | 6 max | About the width of a soda can |
| Rail height, lowest mattress setting | 26 min | 66 min | Top of rail to top of mattress support |
| Rail height, highest mattress setting | 9 min | 23 min | Top of rail to top of mattress support |
The rail heights are measured to the mattress support, not to the top of the mattress. With a 6 in mattress in the lowest position, the rail stands at least 20 in (51 cm) above the sleeping surface. In the highest (newborn) position it can be as little as 3 in above a thick mattress, which is why the mattress has to come down before a baby can sit or pull up.
Most mattresses are sold as 28 × 52 in (71 × 132 cm), just under the crib's inside size so a fitted sheet can go on. Thickness ranges from about 4 in for firm foam to the 6 in limit for innerspring and hybrid models.
Crib mattress size chart
Only the full-size mattress is effectively standardized. Mini crib, play yard and bassinet pads vary by brand, and a pad that is even an inch too small leaves a gap where a baby's face can get trapped.
| Mattress | Typical size (in) | Typical size (cm) | Thickness | Standardized? |
|---|---|---|---|---|
| Full-size crib (US) | 28 × 52 | 71 × 132 | 4-6 in | Yes, min 27¼ × 51⅝ in |
| Mini crib (US) | 24 × 38 | 61 × 97 | 3-5 in | No, sizes vary by maker |
| Play yard pad | About 27 × 38 | About 69 × 97 | 1-1.5 in | No, model-specific |
| Bassinet pad | About 15-18 × 30-33 | About 38-46 × 76-84 | 1-1.5 in | No, model-specific |
| Cot (UK/EU) | 23.6 × 47.2 | 60 × 120 | About 4 in (10 cm) | De facto standard |
| Cot bed (UK/EU) | 27.6 × 55.1 | 70 × 140 | About 4-5 in (10-13 cm) | De facto standard |
Use only the pad that came with a play yard or a replacement the manufacturer names for that model. A generic "mini" mattress can be the wrong size by an inch or more, and stacking a second mattress on the thin original pad is a known suffocation hazard.
Checking the mattress fit
Push the mattress into one corner of the crib. If you can fit more than two fingers (about 1½ in, 4 cm) into the gap at the opposite side or end, the mattress is too small for that crib. A mattress that has to be forced in is too big and will bow up at the middle.
Standard crib vs mini crib dimensions
A mini crib is any crib with an interior shorter than 49¾ in or narrower than 25⅜ in. That definition, from the federal non-full-size crib rule, is why mini cribs and play yards have their own standard (ASTM F406) and their own mattresses.
| Type | Length | Width | Height | Usually lasts to |
|---|---|---|---|---|
| Full-size / convertible crib | 53-57 in (135-145 cm) | 29-31 in (74-79 cm) | 34-46 in (86-117 cm) | About 2-3 years, then toddler bed |
| Mini crib | 38-42 in (97-107 cm) | 24-27 in (61-69 cm) | 33-40 in (84-102 cm) | About 18-24 months |
| Play yard | About 38-40 in (97-102 cm) | About 28 in (71 cm) | About 29-30 in (74-76 cm) | 35 in tall or 30 lb, typical label limits |
A mini crib saves about 4 sq ft of floor (roughly 7.2 sq ft against 11.3 sq ft for the footprints shown). That matters in a shared bedroom or a closet-sized nursery, but most children outgrow a mini crib's length a year or more before a full-size one.
UK and European cot sizes in cm
Outside North America, a crib is called a cot, and the common sizes are metric. A cot takes a 60 × 120 cm mattress and usually measures about 66 × 126 cm outside. A cot bed takes a 70 × 140 cm mattress, measures about 77 × 146 cm outside, and converts into a junior bed for children up to about 4 to 6 years old.
The 70 × 140 cm cot bed mattress is close to a US crib mattress (71 × 132 cm) in width but 8 cm (about 3 in) longer, so US crib sheets do not fit it. Cots sold in the UK and EU follow BS EN 716 rather than the US rules.
Lowering the mattress and when a child outgrows the crib
- Newborn: the highest mattress position is fine while the baby cannot roll over or push up, and it saves your back.
- Sitting up (often around 5-6 months): drop to a middle position.
- Pulling to standing: move to the lowest position, which gives the full 26 in of rail measured from the support, or about 20 in above a 6 in mattress.
- Time to move out: common pediatric guidance is to switch when the child is about 35 in (89 cm) tall or starts climbing out, whichever comes first. The top rail is then too low relative to their height.
Most convertible cribs turn into a toddler bed by swapping one side for a short guardrail. The mattress stays the same 28 × 52 in, so the next step costs nothing in bedding. Sizes and limits for that stage are on the toddler bed sizes page.
Converting to a full-size bed
A "4-in-1" crib's last stage is a full (double) bed. That needs a conversion rail kit and a 54 × 75 in (137 × 191 cm) mattress, and the finished bed is roughly 56 × 78 in (142 × 198 cm) on the floor, more than twice the crib's footprint. Check the room size before counting on that stage. The mattress size chart lists twin and full sizes for the big-kid bed.
Planning space around the crib
- Access side: leave 30-36 in (76-91 cm) of clear floor along the side you lift from. You need room to bend with a baby in your arms.
- Windows and cords: keep the crib well away from windows and from any blind or curtain cord a standing toddler could reach.
- Gaps against the wall: push the crib fully against the wall or leave a clear gap a child cannot get wedged in, and keep other furniture out of reach of the rail.
- Door swing: a 54 in crib on a 10 ft wall leaves about 66 in for a dresser and the door, so measure the door's swing first.
A practical minimum nursery is about 7 × 9 ft for a crib and a small dresser. Add a glider or rocker (roughly 30 × 34 in, plus space to rock) and you want closer to 9 × 10 ft. For dresser stability rules and other furniture sizes, see kids' furniture dimensions and the general dresser size guide.
Buying a used or older crib
Every crib made or sold in the US since June 28, 2011 must meet the current federal standard. That rule banned drop-side cribs, which had been linked to deaths when the moving side came loose. An older crib may still have the right dimensions but miss the newer hardware, slat strength and testing rules.
Safe to reuse if
- It was made after June 2011 and has its label
- No slat, post or hardware is missing or cracked
- Slats are no more than 2⅜ in (6 cm) apart
- Corner posts do not rise above the end panels by more than about 1/16 in (1.5 mm)
Do not use if
- It has a drop side or was recalled
- It needs parts from a hardware store to hold together
- It has decorative cutouts in the headboard
- The mattress gap fails the two-finger test
When the crib is set up, the car seat and the stroller are usually the next items to size. See car seat dimensions and the high chair size guide for the feeding stage.
Frequently asked questions
What is the size of a standard crib in feet and inches?
The sleeping area is 28 × 52 in, which is 2 ft 4 in × 4 ft 4 in. With rails and posts, most full-size cribs take up about 2 ft 6 in × 4 ft 6 in of floor (30 × 54 in, 76 × 137 cm).
Are all US crib mattresses the same size?
Full-size ones are close. Federal rules require at least 27¼ × 51⅝ in and at most 6 in thick, and most are sold at 28 × 52 in. Mini crib and play yard mattresses are not standardized, so buy the one the crib maker specifies.
What are crib sizes in cm?
A US full-size crib mattress is about 71 × 132 cm. UK and European cots use 60 × 120 cm mattresses, and cot beds use 70 × 140 cm. A US mini crib mattress is about 61 × 97 cm.
Do sheets for a standard crib fit a mini crib?
No. A mini crib mattress is about 4 in narrower and 14 in shorter than a standard one, so a standard fitted sheet bunches up and can come loose. Use sheets labeled for mini cribs, or for the exact model.
How much room does a crib need in a nursery?
Plan on the crib footprint (about 30 × 54 in) plus a 30-36 in (76-91 cm) clear zone along the side you lift the baby from. A nursery of about 9 × 10 ft holds a crib, a dresser and a glider without crowding.
Can a crib mattress be thicker than 6 inches?
Not for a full-size crib. The 6 in limit keeps enough rail height above the mattress. Thicker mattresses and added toppers reduce that height and should not be used.