Mattress Topper Sizes: Cal King, Twin XL and Odd-Size Fits

Ordering a queen topper for a queen bed is easy. The trouble starts with the in-between beds: a California king that is longer and narrower than a king, a dorm twin XL, a camper bed that is a few inches short, or an antique frame that matches no modern standard. Knowing the common mattress topper sizes and how to measure your own bed saves you from a topper that hangs over the edge or leaves a gap at the headboard.

The short answer: measure the width and length of your mattress, not the frame, and compare those numbers to the standard dimension chart. If your bed matches a standard size, buy that size. If it falls between sizes, buy the next size up and trim foam or latex to fit. Fiber and wool toppers are harder to cut cleanly, so for odd beds those are better ordered in custom sizes.

Thickness matters too, because a thick topper on a deep mattress may need new fitted sheets. Standard dimensions, the hard-to-fit beds and a clean way to trim foam at home are all covered here.

Standard Mattress Topper Sizes Chart

Topper dimensions in the United States usually match mattress dimensions. Some toppers run about half an inch smaller on each side so they sit neatly inside the mattress edge.

Names cause some confusion. A single mattress topper is the same as a twin in the United States. A double bed topper is the same as a full, so a mattress topper double listing should measure 54 by 75 inches. If you see metric sizes, the product may be built for a European or UK bed, which uses different dimensions, so always confirm the inches.

How to Measure Your Mattress

Never assume the size from the bed frame or an old sheet label. Mattresses shrink slightly as foam compresses, and older or custom beds may not match the chart at all.

1. Strip the bed. Remove sheets, pads and any existing topper.
2. Measure the width. Run a tape across the middle of the mattress from edge to edge.
3. Measure the length. Run the tape from head to foot along the center.
4. Measure the depth. Measure from the bottom seam to the top surface at a corner.
5. Check the corners. Note whether corners are square or rounded, which is common in RV and boat mattresses.
6. Write it down. Round to the nearest half inch and compare to the chart.

Add the topper thickness to the mattress depth to find the sheet pocket depth you need. A 12 inch mattress with a 3 inch topper needs sheets that fit at least 15 inches, and a bit more is better.

California King Mattress Topper Fit

A California king mattress topper measures 72 by 84 inches, 4 inches narrower and 4 inches longer than a standard king. Putting a standard king topper on a Cal king leaves 2 inches of overhang on each side and a 4 inch gap at the foot. It looks sloppy and the overhang can slide off during the night.

If you already own a king topper and need it to fit a Cal king, trimming the width is possible, but you cannot add length. Buy the correct size when you can. Cal king options are slightly less common, so it pays to confirm the dimensions in the listing rather than trusting the product title.

Twin XL and Full XL Toppers

A twin XL mattress pad or topper is 5 inches longer than a regular twin, which suits college dorm beds and taller kids. Most dorm beds are twin XL, so check before move-in day. A regular twin topper on a twin XL bed leaves a noticeable gap.

Two twin XL toppers side by side also equal a king width and length (76 by 80 inches). That setup is popular for split king adjustable beds, where each side moves independently and a single topper would bunch in the middle.

A full XL mattress topper, at 54 by 80 inches, is less common. Some sellers carry it; otherwise buy a queen and trim 6 inches from the width, which works well with foam or latex.

RV, Short Queen and Custom Sizes

Campers and travel trailers often use beds that are shorter or narrower than home mattresses. The most common is the short queen at about 60 by 74 or 75 inches. An RV mattress topper built for that size fits much better than a standard queen, which overhangs the foot and can block storage lids or slide-out mechanisms.

Other RV and boat beds include three-quarter sizes, bunk sizes around 28 to 34 inches wide, and V-berths with angled or curved corners. For these, you have two good options:

• Buy a custom size mattress topper. Several makers cut foam or latex to your exact dimensions, including angled corners. It costs more but fits perfectly.
• Trim a standard topper. Buy the smallest standard size that covers your bed, then cut it to shape at home.

A short queen mattress topper is worth the search for anyone who camps often, because a well-fitted topper also stays in place on bumpy roads.

How to Trim a Foam Topper to Fit

Memory foam and latex cut cleanly with the right tools. Polyester fiber, feather and wool toppers do not, because the fill spills out of an open seam.

Tools and Materials

• Electric carving knife or long serrated bread knife
• Tape measure and straightedge (a long level or board works)
• Marker or chalk
• Painter’s tape
• Cut-resistant gloves
• A large, flat work surface

Steps

1. Let it expand. Allow a compressed topper 24 to 48 hours to reach full size before measuring.
2. Remove the cover. If the topper has a zippered cover, take it off. You will need to buy or sew a smaller one.
3. Measure and mark. Lay the topper flat, measure from the factory edge and mark a line. Double check before cutting.
4. Tape the line. Painter’s tape on both faces helps guide the blade and reduces tearing.
5. Cut slowly and straight down. Keep the blade vertical and use long, steady strokes. An electric knife gives the cleanest edge.
6. Round corners if needed. Trace the old mattress corner or a template and cut in short strokes.
7. Test the fit. Place it on the bed and trim small amounts if needed.

Keep fingers well clear of the blade path, unplug electric knives when setting them down, and work on a stable surface. Cutting leaves foam crumbs, so vacuum the area when you finish.

Troubleshooting Size Problems

The topper slides off. It may be too small, or the sheet is too shallow. Use deep pocket sheets or elastic corner straps.

It overhangs the edge. The topper is too large. Trim foam or latex, or return it for the correct size.

There is a gap at the headboard. The topper is too short, often a twin on a twin XL or a king on a Cal king. Buy the correct length; filler strips rarely stay put.

Sheets will not stretch over it. Measure combined depth and buy sheets with a larger pocket.

General Cost Ranges

Price scales roughly with surface area. Twin and twin XL toppers are the least expensive, full and queen fall in the middle, and king and Cal king cost the most. A king size mattress pad or topper can cost 30 to 50 percent more than a queen of the same material. Uncommon sizes like full XL and short queen often carry a small premium, and fully custom cuts can cost significantly more than a standard size. Trimming a standard foam topper at home is usually the cheapest route to an odd fit.