How to Measure for Custom Cushions | Fit That Lasts for Years

Getting the wrong size for a replacement cushion is a frustrating, expensive mistake. Whether you’re ordering for a patio set or indoor furniture, the approach to measuring for custom cushions comes down to a few basic rules: record the widest usable surface, skip the decorative edging, and follow the vendor’s form exactly. Here’s how to do it without a second try.

What You Need Before You Start

Grab a cloth tape measure (the flexible kind used for sewing), a notepad, and a pen. A metal tape works but is harder to bend around curves. You’ll also need a flat surface if the cushion is still on the furniture.

Most importantly, read the vendor’s measurement instructions before you touch anything. Sellers measure differently, so follow their form precisely. One trusted source from BBQGuys’ patio cushion measuring guide instructs users to measure across the widest part from seam to seam, explicitly noting not to include welting. Foam By Mail’s guide adds that you should lay the cover flat, smooth wrinkles without stretching, and measure across the center instead of along edges or corners.

Measuring Standard Rectangular Seat Cushions

For a standard rectangular seat cushion, you need three dimensions: width, depth, and thickness. These three are the only ones needed for this shape.

• Width: Measure left to right across the widest point of the seating area, from seam to seam.
• Depth: Measure front to back, again at the widest or center point where the seat is usable.
• Thickness: Measure top to bottom at the thickest point of the cushion, straight down through the middle.

When taking these numbers, keep the tape flat and level. If the cushion is installed, measure the seating area of the furniture itself if the old cushion is misshapen or compressed.

Back Cushions, Rounds, and Odd Shapes

Back cushions take width, height, and thickness. If the back cushion sits on top of the seat cushion, subtract the seat cushion’s thickness from the back height so the finished back doesn’t stand too tall.

For round cushions, measure the diameter at the widest point. Sectional sets work differently: measure the entire set’s width and let the vendor divide it into individual cushions when you request it. Irregular shapes—trapezoids, T-shapes, curves—need multiple measurements. Foamorder.com recommends sketching the shape and providing a template for curves and angles; that template is often the only reliable way to match a non-rectangular cushion.

One rule applies to every shape: measure the seating area itself, never over the piping, fringe, or welting. That decorative edge adds an inch or more to each side, and a cushion built to that number will be too big.

Commons Mistakes and Fit Details Worth Knowing

Several errors trip up first-timers. Measuring over the welting instead of seam-to-seam inflates every dimension. Measuring the foam instead of the cover gives you the wrong size for a replacement. Skipping the asymmetrical check on an old, worn cushion guarantees a poor fit.

Two more details matter. Some vendors accept only whole or half-inch increments, so round to the nearest acceptable number per their instructions. Fit conventions vary too: standard bench pads run 2–3 inches thick, while deep-seating cushions often start at 4–6 inches. When in doubt, follow the vendor’s form exactly and call their support line if your numbers feel off.

Once you’ve got your measurements locked in, see our picks for the best custom cushions to find a maker ready for your dimensions.

Measuring for custom cushions takes ten minutes and one careful pass with a tape measure. Write the numbers down in the exact order the vendor lists them, round to their acceptable increments, and double-check your work before submitting. A little care up front means cushions that fit right, look right, and last.