How to Choose the Right Size Crib Sheet for Your Mattress

Quick answer

Measure your mattress length, width, and depth before you buy. A standard crib mattress is typically 52 x 28 inches, but mini cribs, bassinets, and playards each use different dimensions. Choose a sheet labeled for your exact sleep space with a continuous elastic hem, and size down if your mattress is thinner than average.

A crib sheet that looks right on the shelf can still bunch, pop off, or leave gaps once it is on the mattress. The fix is not brand loyalty or thread count. It is matching the sheet's cut to your mattress length, width, and depth, then checking that the elastic actually grips.

This guide walks through the measurements that matter, how to read labels for cribs, mini cribs, bassinets, and playards, and when a muslin or cotton sheet is the better pick. You will also see how real sheets from Under the Nile are sized so you can compare them to your own mattress.

Measure the mattress, not the crib frame

Crib frames are built to hold a mattress, but the mattress itself is what the sheet wraps. Use a tape measure on the mattress top for length and width, then measure the depth from the top surface down to the bottom edge. Write those three numbers down before you shop.

A standard crib mattress size is generally 52 inches long by 28 inches wide, but depth varies by brand and model. If your mattress is thinner than about 5 inches, a standard fitted sheet may have too much slack. If it is thicker, the sheet may not reach under all four corners.

• Measure length, width, and depth in inches, then convert to centimeters if the sheet lists metric sizes.
• Re-measure after any mattress change, even if the crib frame is the same.

Match the sheet label to the sleep space

Crib, mini crib, bassinet, and playard sheets are not interchangeable. A standard crib sheet will be far too large for a bassinet, and a playard sheet may be too small for a full crib mattress. Look for the sleep space name on the packaging or product page before checking the dimensions.

For playards, the sheet must fit the playard mattress or pad, not the playard floor. Under the Nile lists its Playpen / Playard Sheet - Hearts and Muslin Playpen/Playard Sheet - Kites as playpen and playard sheets, while the Muslin - Bassinet Sheet - Clouds is sized for most bassinets at 65cm x 45cm. Those are different products for different footprints.

• Never stretch a larger sheet onto a smaller mattress to make it fit.
• If the label says crib but your sleep space is a playard, keep looking.

Check the elastic and the fit test

A fitted crib sheet needs elastic all the way around, not just at the corners. A continuous elastic hem pulls the fabric under the mattress evenly and helps the sheet stay put as your baby moves. Corner-only elastic can leave loose fabric along the sides.

After you put the sheet on, press your palm across the center and along each edge. The fabric should feel taut, not drum-tight, and no corner should lift when you tug gently. If you can pinch more than a small fold of fabric, the sheet is too big for that mattress.

• Do the tug test at all four corners before the first sleep.
• Wash and dry the sheet once, then re-check the fit, because shrinkage can change it.

Choose the fabric for your climate and routine

Organic Egyptian cotton is a common choice because it is soft and breathable. Muslin is a looser weave that feels lighter and airier, which many parents prefer for warm rooms or layered bedding. Both can be safe when they fit correctly, but the fabric changes how the sheet feels and how it wears.

Under the Nile's Crib Sheet - Shadow Floral is made from 100% organic Egyptian cotton and fits most crib mattresses at 130cm x 90cm, with a continuous elastic hem. The Muslin - Bassinet Sheet - Clouds uses 100% organic Egyptian muslin and is described as lightweight and breathable, making it a good cover for cool summers and warm winters. If your priority is a snug, smooth surface, cotton is the simpler pick. If you want airflow and a softer drape, muslin is worth trying.

• Cotton tends to feel smoother and more structured; muslin feels lighter and slightly textured.
• Buy two sheets per sleep space so one can be in the wash.

Allow for shrinkage and check the size chart twice

Many crib sheets are sized to allow for shrinkage, which means they may arrive slightly larger than the mattress and tighten after the first wash. That is normal, but it also means you should not buy a sheet that is already too small. Check the product page for a stated size or a note about shrinkage.

If a product page does not list a size, treat that as a missing detail rather than a guess. Contact the seller or choose a sheet with published measurements. Under the Nile lists specific dimensions for several sheets, so you can compare those numbers directly to your mattress before ordering.

• Wash in cold or warm water and dry low to limit excess shrinkage.
• Keep the packaging or order details until you have confirmed the fit.

Decision rules for buying the right crib sheet

• If you have a standard crib mattress: Measure it, then choose a sheet labeled for cribs and sized near 130cm x 90cm. Under the Nile's Crib Sheet - Shadow Floral lists that size and a continuous elastic hem. Confirm the depth is within the sheet's range before ordering.
• If you have a mini crib or playard: Do not use a standard crib sheet. Choose a sheet labeled for a mini crib or playard, like the Playpen / Playard Sheet - Hearts or the Muslin Playpen/Playard Sheet - Kites. A playard sheet is cut for a smaller, often thinner pad, so fit will be tighter and safer.
• If you have a bassinet: Use a bassinet-specific sheet such as the Muslin - Bassinet Sheet - Clouds, which is sized for most bassinets at 65cm x 45cm. A crib sheet will be far too large and can create loose fabric.
• If the product page lists no size: Treat that as a missing detail. Ask the seller for the exact length, width, and depth, or choose a sheet with published measurements. Never guess on a sleep surface.

Real sheets and what their specs tell you

• Crib Sheet - Shadow Floral: Made from 100% organic Egyptian cotton, fits most crib mattresses at 130cm x 90cm, and has a continuous elastic hem. This is the closest match for a standard crib mattress, and the continuous elastic hem is the feature that helps the sheet stay snug.
• Muslin - Bassinet Sheet - Clouds: Made from 100% organic Egyptian muslin and sized to fit most bassinets at 65cm x 45cm. A bassinet is much smaller than a crib, so this sheet will not fit a standard crib mattress. The muslin weave is lightweight and breathable.
• Playpen / Playard Sheet - Hearts: A 100% organic Egyptian cotton playpen and playard sheet with a fitted elastic design and a neutral heart print. Playard mattresses are smaller and often thinner than crib mattresses, so use a sheet labeled for a playard rather than stretching a crib sheet.
• Muslin Playpen/Playard Sheet - Kites: A 100% organic Egyptian muslin playpen and playard sheet with a fitted elastic design and a fresh kite print. If you want the lighter feel of muslin in a playard, this is the matching option. It is sized for a playard, not a full crib.

Who this sizing approach is for

Best for

• Parents setting up a first crib, mini crib, bassinet, or playard who need to match a sheet to a specific mattress
• Caregivers replacing a sheet that bunches, pops off, or leaves gaps
• Shoppers comparing cotton and muslin sheets for a nursery

Not for

• Anyone looking for a decorative sheet that does not need to fit a sleep surface
• Buyers who already have a sheet that fits correctly and only want a different print
• People shopping for adult beds or non-standard custom mattresses

The right crib sheet is the one that matches your mattress measurements and stays taut after washing. Measure first, choose the sheet labeled for your sleep space, and check the fit at every corner. If you are unsure between two sizes, size down or ask for the exact dimensions before you buy.