Knife Edge Back Cushions

A Fluff Haus guide · Hickory, North Carolina · Updated October 18, 2026

Measure what the new cushion needs to fit. An old insert may have compressed; a stuffed cover may bulge. For a cover you plan to keep, use its empty, unstretched dimensions and check them against the furniture.

No measurements yet? Start with a question or a description of the problem.

Before you begin

• A tape measure, a flat surface and a simple sketch.
• The empty cover, if removable, plus access to the furniture platform.
• A label for each position: left, center or right, viewed while facing the furniture.

Use inches and record fractions rather than rounding to a standard size. Do not add an allowance for fullness, seams or piping unless the workroom instructs you to.

1. Record the seat cushion dimensions

1. Remove the insert. Close the zipper and lay the empty cover flat without pulling it tight.
2. Measure the width from side seam to side seam.
3. Measure the depth from front seam to back seam.
4. For a boxed cushion, measure the border panel from its upper seam to its lower seam for thickness.
5. Record whether the front and back widths differ, and whether corners are rounded or notched.

2. Measure backs separately

Record width from side to side, height from bottom to top, and thickness separately. Note how the back sits: on top of a seat, behind it, or between arms. Do not substitute seat depth for back height. Photograph the back in place so the workroom can see its intended relationship to the seat.

3. Check the furniture opening

Measure the usable platform from side to side and front to back. Note arms, trim, hardware and spaces that narrow toward the back. If the furniture has several cushions, check each position; they may not be identical. Compare these measurements with the covers and explain any discrepancy instead of averaging it away.

4. Knife-edge cushions need a different thickness reference

A knife-edge cushion has no separate border panel. Record the flat cover dimensions and describe the desired fullness or center loft separately. A measurement taken across a bulging, filled cushion is not the same as a flat cover measurement. Ask the workroom which finished-thickness reference is needed for the construction.

5. Draw T-shapes, L-shapes and curves

Draw a top view with the front clearly marked. Label the overall width and depth, main body, each projection or notch, and the location of rounded corners. Include thickness separately. Do not assume matching-looking wings have matching dimensions.

A photo cannot establish an exact curve or scale. Ask whether a full-size template is needed. If a template or old cushion is requested, confirm the method, address and whether it will be returned before sending anything.

6. Take three useful photos

• The furniture with cushions in their normal positions.
• The empty seating platform or backrest.
• The cushion or empty cover from above and from the side, with unusual seams and corners visible.

Copy this checklist

• Furniture type and cushion position.
• Seat or back; quantity.
• Existing cover dimensions: width × depth or height × thickness, where applicable.
• Furniture opening dimensions.
• Shape, front edge, corners and any ties.
• Keeping existing covers, supplying COM, or requesting new fabric.
• What feels wrong with the current cushion.

Common mistakes

Measuring over a stuffed curve, using old foam alone, stretching the cover, swapping back height with seat depth, assuming every position is identical, or adding a blanket oversizing allowance can all lead to a poor fit.

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