Project: Envelope Pillowcase

What an Envelope Pillowcase Is (and Why Beginners Love It)

An envelope pillowcase is a removable pillow cover that closes in the back using overlapping fabric panels—like an envelope flap. Instead of a zipper, buttons, or snaps, the back is made from two pieces that overlap enough to keep the pillow insert tucked inside. This makes the project beginner-friendly because you can focus on straight seams and neat hems while still ending up with a professional-looking cover.

You will sew three main pieces: one front panel and two back panels. The back panels each have a finished hem on one long edge. When assembled, those hemmed edges overlap at the center back, creating the “envelope” opening. The pillow insert slides in and out easily, and the overlap keeps it from peeking out during use.

This project is also a great way to practice accuracy and consistency: matching corners, keeping seam allowances even, and making hems that look crisp. You can make envelope pillowcases for couch pillows, bed shams, seasonal decor, or gifts. Once you know the formula, you can scale it to any pillow size.

What You’ll Make and What You’ll Need

Finished item

One envelope pillowcase sized to fit a pillow insert (for example, a 16 in x 16 in or 18 in x 18 in insert). For a plump look, many people use an insert that is 1–2 inches larger than the cover size, but you can also match insert and cover sizes for an easier fit. Choose one approach and be consistent.

Materials

• Woven fabric (quilting cotton, cotton-linen blends, lightweight canvas, or home decor cotton). Avoid very stretchy knits for your first one.
• Matching thread.
• Pillow insert in your chosen size.
• Optional: fusible interfacing (lightweight) if your fabric is very thin and you want more body.

Tools

• Fabric shears or rotary cutter and mat.
• Ruler or measuring tape.
• Marking tool (chalk or washable marker).
• Pins or clips.
• Iron and ironing board.
• Sewing machine.

Choosing a Size and Calculating Your Cut Pieces

The simplest way to draft an envelope pillowcase is to start with your pillow insert size. Let’s call the insert width and height P (for a square pillow, both are the same). The cover will be made from:

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• Front panel: one piece cut to P x P (plus seam allowance on all sides).
• Back panels: two pieces cut to P x (half of P plus overlap) (plus seam allowance). Each back panel will have a hem on one long edge.

The key design choice is the overlap. A common overlap is 4–6 inches total. That means the two back pieces overlap each other by that amount when laid on top of the front. More overlap keeps the insert more secure and prevents gaping.

A reliable formula (works well for beginners)

Use these assumptions:

• Seam allowance: 1/2 inch on all sides.
• Hem on each back panel: a double-fold hem, 1/2 inch + 1/2 inch (so the raw edge is fully enclosed).
• Total overlap: 5 inches (a good middle ground).

For a pillow insert size P x P:

• Front cut size: (P + 1) x (P + 1) because you add 1 inch total for seam allowances (1/2 inch each side).
• Each back panel cut size: (P + 1) wide by ( (P + 5) / 2 + 1 ) tall? Let’s break it down clearly using the direction the overlap runs.

Most envelope pillowcases have the overlap running vertically when the pillow is upright, meaning the back panels overlap left-to-right. In that common layout:

• The height of all pieces matches the pillow height.
• The width is where the overlap happens.

So for a square pillow P x P:

• Front panel cut: (P + 1) wide x (P + 1) tall.
• Back panels cut (2 pieces): each is ( (P + 5) / 2 + 1 ) wide x (P + 1) tall.

Explanation: the finished back width needs to cover the pillow width plus overlap. If the finished pillow width is P, and you want 5 inches of overlap total, the combined finished widths of the two back panels should be P + 5. Each panel contributes half of that: (P + 5)/2. Then add 1 inch total seam allowance to the width (1/2 inch on each side), giving (P + 5)/2 + 1.

Example: 18 in x 18 in pillow

• Front cut: 19 in x 19 in.
• Back panels cut: each ( (18 + 5)/2 + 1 ) = (23/2 + 1) = 11.5 + 1 = 12.5 in wide x 19 in tall. Cut two pieces: 12.5 in x 19 in.

When finished, each back panel will lose 1 inch total width to seam allowances (1/2 inch on each side), so each becomes 11.5 inches finished width. Two panels together equal 23 inches, which is 18 inches plus 5 inches overlap.

Rectangular pillows

For a rectangle, use width W and height H. Keep the overlap along the width (left-to-right) unless you prefer it along the height. With overlap along width:

• Front cut: (W + 1) x (H + 1).
• Back panels cut: each ( (W + overlap)/2 + 1 ) x (H + 1).

Choose overlap 5 inches as a default, or 6–7 inches for larger pillows.

Fabric Planning and Design Options

Print direction

If your fabric has a directional print (text, animals that face one way, stripes), decide which way is “up” on the pillow front. Make sure the back panels are cut so the print is upright when the pillow is finished. For many directional prints, you will cut the back panels with the same “up” direction as the front, which is easy if the overlap runs left-to-right.

Mix-and-match backs

You can use the same fabric for all pieces, or choose a coordinating fabric for the back panels. This is a practical way to use smaller cuts of fabric: a feature print on the front and a solid on the back.

Piping or trim (optional)

If you want a more tailored look, you can add piping in the seam between front and back. This is optional and adds complexity. If you are making your first envelope pillowcase, focus on clean hems and accurate assembly first.

Step-by-Step: Sewing the Envelope Pillowcase

Step 1: Cut your pieces

Cut one front panel and two back panels using the measurements you calculated. Keep your pieces labeled (Front, Back A, Back B). If your fabric looks similar on both sides, mark the wrong side with a small piece of painter’s tape or a chalk mark near an edge.

Step 2: Hem the inner edges of the back panels

Each back panel needs a finished hem on one long vertical edge (the edge that will form the envelope opening). Choose the edge that will meet at the center back.

For each back panel:

• With the wrong side up, fold the inner edge over 1/2 inch toward the wrong side. Press.
• Fold over another 1/2 inch to hide the raw edge. Press again.
• Pin or clip the hem in place.
• Stitch close to the inner folded edge (about 1/8 inch from the fold). Keep your stitching straight and consistent.

Practical tip: If your fabric is thick (canvas or upholstery cotton), reduce bulk by making a slightly narrower hem (for example, 3/8 inch + 3/8 inch). The goal is a neat, flat hem that doesn’t create a ridge.

Step 3: Arrange the layers for the envelope back

Lay the front panel right side up on your table. Place Back Panel A right side down on top of it, aligning the outer edges (top, bottom, and one side). The hemmed edge should face toward the center of the pillow. Then place Back Panel B right side down, aligning the remaining outer edges. The two hemmed edges should overlap in the middle.

Check these points before pinning:

• All outer raw edges line up evenly.
• The back panels overlap by your planned amount (approximately 5 inches total in the example).
• The hemmed edges are parallel and not skewed.
• If you have a directional print, confirm it is oriented correctly on the front.

Pin around all four outer edges. Add a few pins across the overlap area to keep the back panels from shifting while you sew.

Step 4: Sew around the perimeter

Sew all the way around the outer edge with a 1/2 inch seam allowance. Start on one side, sew to the corner, pivot, and continue. Backstitch at the beginning and end.

Practical corner tip: Stop sewing 1/2 inch from the edge (or exactly at your seam allowance distance), keep the needle down, lift the presser foot, rotate the fabric 90 degrees, lower the presser foot, and continue. This keeps corners square and consistent.

Step 5: Reinforce the envelope opening area (recommended)

The envelope opening gets extra handling when you insert and remove the pillow. To strengthen it, sew a short reinforcing line near the side seams where the hemmed edges end.

Two easy options:

• Extra backstitching: When you sew the side seams, backstitch a few extra stitches right where you cross the hemmed edge area.
• Short bar tack: After sewing the perimeter, stitch a short, dense zigzag (or a very short straight stitch) across the seam allowance at the point where the hem meets the side seam. Do this on both sides.

Keep reinforcement within the seam allowance so it won’t show on the finished pillow.

Step 6: Trim and turn right side out

Trim seam allowance bulk at the corners to help them turn neatly. Cut diagonally across each corner, being careful not to cut through your stitching. Then turn the pillowcase right side out through the envelope opening.

Use a blunt tool (like a chopstick or a point turner) to gently push out the corners. Avoid sharp objects that could poke through the fabric.

Step 7: Press for a crisp finish

Press the pillowcase flat, focusing on the outer edges and corners. Make sure the seam sits right at the edge and doesn’t roll to the front or back. Press the envelope overlap area so it lies flat and looks intentional.

Step 8: Insert the pillow form

Fold the pillow insert slightly and slide it into the cover through the envelope opening. Work the corners of the insert into the corners of the cover. Adjust the overlap so it sits centered on the back.

Fit and Finish: Getting a Professional Look

How tight should it be?

A good envelope pillowcase looks smooth on the front without sagging, and the corners look filled. If your cover is too loose, the front may wrinkle and the insert may shift. If it is too tight, seams may strain and corners may distort.

Practical guideline:

• If you want a very full, “designer” look, make the cover the same size as the pillow insert or up to 1 inch smaller in each direction (this depends on fabric thickness and insert loft). For beginners, matching the insert size is simplest.
• If you are using a thick fabric, avoid making the cover smaller than the insert; thickness already reduces interior space.

Topstitching the outer edge (optional)

If you like a crisp, tailored edge, you can topstitch around the perimeter after turning right side out and pressing. Stitch 1/8 inch to 1/4 inch from the edge. This helps the seam stay flat and adds a decorative detail. Use a slightly longer stitch length for a clean look.

Matching stripes or checks

If your fabric has stripes or checks, align the pattern at the center front and keep it straight along the edges. For the back panels, you can either match the pattern across the overlap (more advanced) or simply keep each panel straight and accept that the overlap won’t match perfectly. The most important beginner win is keeping stripes level and not tilted.

Common Issues and Quick Fixes

Problem: The envelope opening gapes and shows the insert

• Cause: Not enough overlap, or the cover is too tight and pulls the back panels apart.
• Fix: Increase overlap next time (6–7 inches total). If the cover is too tight, consider adding 1/2 inch to the width and height of the front and back pieces (keeping seam allowance the same).

Problem: The back panels don’t meet evenly; overlap is crooked

• Cause: Hemmed edges were not parallel, or pieces shifted while sewing.
• Fix: When pinning, measure from the outer edge to each hemmed edge at top and bottom to ensure symmetry. Add pins across the overlap area before sewing.

Problem: Corners look rounded or empty

• Cause: Too much bulk in seam allowance, corners not pushed out fully, or insert corners not seated.
• Fix: Trim corners carefully before turning. After inserting the pillow, reach in and pull the cover corners outward while pushing the insert corners into place.

Problem: The hem on the back panels waves or puckers

• Cause: Fabric stretched slightly while sewing, or hem not pressed firmly before stitching.
• Fix: Press the hem in two stages and let it cool flat before stitching. Sew without pulling the fabric; guide it gently.

Variations You Can Try After Your First One

Contrast hem detail

Sew the back panel hems with contrasting thread, or add a narrow strip of contrasting fabric as a facing before hemming. This creates a clean accent visible at the envelope opening.

Centered overlap vs. offset overlap

The instructions above create a centered overlap. You can also offset the overlap so the opening sits slightly to one side. This can look more modern and can help hide the opening depending on how the pillow is used.

Flanged edge (simple version)

A flange is a fabric border around the pillow edge, like a small frame. A beginner-friendly way is to cut the front and back pieces larger, sew as usual, then press and topstitch a rectangle 1–2 inches in from the edge. This creates the look of a flange without adding separate pieces.

Reference Measurements (Quick Table)

These examples assume 1/2 inch seam allowance and 5 inches total overlap, with overlap running left-to-right on the back.

• 16 in pillow: Front cut 17 x 17; Back cuts ( (16+5)/2 +1 ) = 11.5 +1 = 12.5 wide x 17 tall (cut 2).
• 18 in pillow: Front cut 19 x 19; Back cuts 12.5 wide x 19 tall (cut 2).
• 20 in pillow: Front cut 21 x 21; Back cuts ( (20+5)/2 +1 ) = 12.5 +1 = 13.5 wide x 21 tall (cut 2).

If you prefer a larger overlap (6 inches), add 1/2 inch to each back panel width compared to the 5-inch overlap formula.