How to Make a 20×20 Pillow Cover | Envelope Back Secrets

An envelope-style 20×20 pillow cover needs one front panel plus two overlapping back panels, and it takes most sewers under an hour.

Making your own 20×20 pillow cover is one of the quickest wins in home sewing. You cut three rectangles, hem two edges, and sew around the outside. The envelope back means no zippers or buttons, so the whole project is beginner-friendly. The finished cover slips over your insert in seconds and hides the opening neatly at the back.

What Size Fabric Do You Need For A 20×20 Cover?

For a 20×20 pillow cover, you need a 20-inch front square and two back rectangles. The back pieces need extra length for the overlap that forms the envelope opening. Most tutorials use one of these cut sizes:

• One-piece envelope: a single 20 x 46-inch piece folded over the insert.
• Three-piece envelope: one 20 x 20 front panel plus two 20 x 15 back panels.
• Larger overlap: one 20 x 20 front plus two 20 x 16 back panels for a deeper overlap.

The math behind the three-piece version is simple: for a 20-inch square, each back panel is 10 inches (half the pillow width) plus 5 inches of overlap, which gives you 15 inches per piece. If you want a more generous overlap, add an extra inch to each back panel.

How Much Fabric Does A 20×20 Pillow Cover Use?

Your yardage depends on the fabric width and whether you’re matching a pattern. That one cut gives you the 20 x 46-inch strip for the one-piece method, or the front and back panels for the three-piece version.

If you’re working with patterned fabric that needs matching across the seams, buy extra — pattern matching can easily require a full yard or more. The 3/4-yard figure assumes plain fabric and no matching worries.

How To Sew A 20×20 Pillow Cover Step By Step

Start by washing, drying, and ironing your fabric so it won’t shrink after you finish the cover. Then follow this order:

1. Cut your pieces: cut one 20 x 20 front square and two 20 x 15 back rectangles (or the larger 20 x 16 version).
2. Hem the back panels: on one long edge of each back piece, fold and press the edge over 1/2 inch twice. Sew along the fold with a 1/4 inch seam allowance. Repeat for the second back panel.
3. Layer the pieces: place the front panel face up. Lay the two back panels on top, face down, with the hemmed edges overlapping in the middle. Both raw edges should be even with the front panel’s edges.
4. Sew the perimeter: sew all the way around with a 1/2 inch seam allowance. Backstitch at the beginning and end so the threads hold.
5. Clip the corners: snip across each corner diagonally, close to the stitch line but not through it, so the corners turn out sharp.
6. Turn and press: reach through the envelope opening and pull the cover right side out. Press all seams flat, and you’re done.

For a sturdier edge that resists fraying, run pinking shears along the raw seams before turning. A down insert will give your finished cover more loft and fluff than a polyester one, which is worth knowing if you want a plump look.

If you’re shopping for inserts and want suggestions that hold their shape well, our roundup of the best 20×20 couch pillows covers tested options that work with this cover size.

How Do You Measure A Pillow Insert Correctly?

Lay the pillow flat on a hard surface and measure seam-to-seam, both horizontally and vertically. Don’t measure corner-to-corner — that gives you a diagonal reading that’s far larger than the actual pillow size. Measuring seam-to-seam keeps your cover sizing honest.

This deliberate undersizing keeps the pillow full and tailored instead of loose and saggy.

Account for seam allowance too. Add 1 inch total per side to your cutting measurements — 1/2 inch on each edge. If you forget the seam allowance and the hem allowance on the back pieces, your finished cover will come out too small to close properly around the insert.

Because published sizing charts differ slightly by manufacturer and style, you may need to adjust your finished target by up to half an inch. When in doubt, sew one test cover in plain muslin before cutting into your good fabric.