There are two ways to size a futon cover, and you should use both. The fast one: measure the width of the frame’s back panel, arms excluded. If it’s 72–75 inches, you have a Full. If it’s 76–80 inches, you have a Queen. The thorough one: measure the mattress itself in three dimensions — width, length, and thickness — lying flat and fully extended.
The frame check identifies which of the two most common sizes you own in about thirty seconds. The mattress measurements confirm it and catch everything the frame can’t tell you.
The quick check: Full or Queen?
Most futon covers sold are one of these two sizes, and most people aren’t sure which they have.
On a bifold futon frame, the back panel spans the length of the mattress — the mattress’s long dimension runs side to side across the sofa. That makes the back panel a reliable proxy for mattress length.
Measure the back panel edge to edge, excluding the arms. Then:
| Back panel width | Size |
|---|---|
| 72–75″ | Full |
| 76–80″ | Queen |
Full and Queen futon mattresses differ by five inches in length (75″ vs 80″) and six in width (54″ vs 60″), so this test separates them cleanly. If your back panel measures well outside both ranges, you’re not looking at a standard Full or Queen, and the mattress measurements below are the only way forward.
Measure the panel itself, not the outside of the frame. Arms add width that has nothing to do with the mattress, which is the single most common way this check goes wrong.
Standard sizes
| Size | Dimensions |
|---|---|
| Cot | 30″ × 75″ |
| Twin | 39″ × 75″ |
| Twin XL | 39″ × 80″ |
| Full | 54″ × 75″ |
| Queen | 60″ × 80″ |
| Loveseat | 54″ × 54″ |
| Chair | 28″ × 54″ |
| Ottoman | 28″ × 21″ |
If your mattress measurements land within about an inch of one of these in both width and length, that stock size will fit. Two or more inches off in either direction and you’re in custom territory.
What the frame can’t tell you
The back panel gives you length. It doesn’t give you thickness, and it doesn’t confirm width.
Thickness is the dimension with the least tolerance and the one nobody checks. Mattresses in the same nominal size are sold in a range of thicknesses, and two frames sold as “full futon frame” can hold mattresses that differ by three inches in depth depending on what the buyer chose. A cover cut for a 6-inch mattress on an 8-inch mattress pulls the top panel taut, strains the zipper, and rounds the corners into a pillow shape. The same cover on a 4-inch mattress sags into loose folds along the sides.
The frame deck is also not the mattress. On most bifold frames the deck is deliberately smaller than the mattress so the mattress can flex at the fold without binding. Measuring the deck will under-report width every time.
So: use the back panel to identify the size, then take the tape to the mattress to confirm it and get the thickness.
The three mattress measurements
Strip the cover off, lay the mattress flat on a hard floor, and open it fully.
Width
Measure across the short dimension, outside edge to outside edge, at the widest point. On a used mattress the middle often bulges more than the ends — measure the widest point, not the average, since a cover cut to the average will strain across the middle.
Keep the tape parallel to the floor. A tape that dips over the curve of the edge adds an inch or more of phantom width.
Length
Measure the long dimension the same way, fully extended, corner to corner. If the mattress has a permanent crease from years of folding, measure through the crease with the mattress opened flat, not half-folded.
This number should agree with your back-panel reading. If the panel said Queen and the mattress measures 75 inches long, the mattress and the frame aren’t a matched set — buy the cover for the mattress.
Thickness
Stand the tape vertically against the side of the mattress at the midpoint of the long edge, and measure from the floor to the top surface. Do not measure at a corner — corners compress and under-report.
Round each measurement to the nearest half inch.
Measuring furniture that isn’t a rectangle
Chair, ottoman, loveseat, and daybed pads complicate things because they often have shaped or wedge-cut cushions.
Chair and ottoman pads are frequently trapezoidal rather than square, wider at the front than the back. Measure both the front edge and the back edge, plus the depth front-to-back and the thickness. Four numbers, not three.
Wedge or tapered mattresses — thicker at one end than the other — need a thickness measurement at each end.
Two-piece and three-piece sets (a seat plus a separate back cushion) need each piece measured independently. They take separate covers, not one large one.
For any of these, sketch the shape on paper, write your numbers on the sketch, and photograph it. That drawing is far more useful to a workroom than a list of numbers with no context.
What to record before you order
- Back panel width, arms excluded
- Mattress width, at the widest point
- Mattress length, fully extended
- Thickness, at the center of the long edge
- Mattress type (cotton, cotton-foam, all-foam, innerspring)
- Age and condition
- Any non-rectangular shaping, with a sketch
Items 5 and 6 are not padding. A cotton-fill mattress compresses over the years and rebounds when a fresh cover compresses it — an eight-year-old cotton futon reads thinner today than it will behave under a new snug cover. An all-foam mattress holds its dimensions but resists compression, so its measured thickness has to be respected exactly. Innerspring futons are the least forgiving: the spring unit sets a hard floor on how much the cover can squeeze.
Snug versus loose: decide before you order
Two people can measure the same mattress correctly and want two different covers.
A snug fit looks upholstered. Corners stay sharp, the fabric stays smooth when the futon is used as a sofa, and the whole thing reads as furniture rather than bedding. It takes more effort to install and puts more load on the zipper.
A relaxed fit is easier to get on and off, easier to launder often, and more forgiving on a mattress that changes shape. It also wrinkles more and shows every fold when the futon is upright.
Neither is wrong. But decide first, because it changes how you interpret your numbers — most people who say “the cover was too tight” measured accurately and simply wanted a relaxed fit without knowing there was a choice.
Common measuring errors
Including the arms in the back panel measurement. Arms aren’t mattress. This is the main way the Full/Queen check misfires.
Measuring the frame deck instead of the mattress. The deck is intentionally smaller than the mattress.
Measuring with the old cover on. A tired cover adds bulk in some places and compresses the mattress in others. Take it off.
Measuring a folded mattress. Bifold futons must be opened flat. A folded measurement will be short by several inches.
Measuring on a soft surface. A mattress measured on carpet or on the frame deck spreads differently than one measured on a hard floor. Use the floor.
Using a stretched cloth tape. Fabric tapes stretch with age. Use a steel tape for anything over three feet.
Measuring once. Measure twice, on different days if the mattress is old and has been compressed under a cover for years. Give it a few hours uncovered to relax first.
When your numbers don’t match a standard size
If your measurements fall outside the ranges above — an antique frame, a European import, a built-in window seat, a daybed, a shikibuton, a bench pad — a stock cover will not fit well, and forcing it will fail at the seams.
That’s what cut-and-sew service exists for: a cover made to your exact three (or four) numbers in a fabric you choose. The measuring process is the same one described above; the only difference is that the numbers go on an order rather than into a size chart. If you’re weighing making one yourself instead, how much fabric a futon cover takes walks through the yardage math.
Before you commit to a fabric
Once the size is settled, the remaining variable is the fabric — and color and hand are the two things a screen reproduces worst. Order swatches of your top two or three candidates and look at them in your own room light before placing the full order. It’s the cheapest insurance in the process.
When you’re ready, browse the full range of futon covers with your numbers in hand.
Frequently asked questions
How do I know if my futon is Full or Queen? Measure the width of the frame’s back panel with the arms excluded. 72–75 inches is a Full; 76–80 inches is a Queen. Confirm by measuring the mattress: Full is 54″ × 75″, Queen is 60″ × 80″.
Do I measure the futon mattress or the frame? Both, for different reasons. The back panel identifies the size quickly. The mattress gives you the width and thickness the frame can’t tell you.
Why doesn’t the frame deck match the mattress? On most bifold frames the deck is intentionally smaller so the mattress can flex at the fold without binding.
How much thickness variance can a cover absorb? Roughly an inch in either direction on most constructions, and less on a snug-fitting cover. Beyond that the fit visibly suffers — taut and strained on the thick side, saggy on the thin side.
My mattress measures between two standard sizes. Which do I choose? Size down only if the mattress is soft cotton fill that will compress. For foam or innerspring, size up or go custom — those mattresses won’t yield.
Should I add seam allowance to my measurements? No. Report the finished mattress dimensions. Allowance is the workroom’s job, and adding your own results in a cover that’s too large.
Can I reuse the measurements from my old cover? Only as a cross-check. Covers stretch, shrink, and were sometimes the wrong size to begin with. Measure the mattress.