How to Measure and Replace Deep Seat Patio Cushions

TL;DR: Measuring deep seat cushions comes down to six numbers: the seat width, depth, and thickness, plus the width, height, and thickness of the back pillow. Use a firm tape measure, measure the frame rather than a cushion that has flattened, and round to the nearest inch. If your frame is still solid but the cushions are sagging or faded, replacing just the cushions brings the whole set back to life for a fraction of the cost of new furniture.

Deep seat patio furniture outlives its cushions. The aluminum or resin frame can sit outside for a decade, while the foam flattens and the fabric fades in a few seasons. The good news is that a sagging cushion is not a reason to replace the furniture. It is a reason to replace the cushion, and getting the fit right starts with measuring correctly.

When to replace deep seat cushions instead of the furniture

If the frame is sound, the cushions are the part worth renewing. Replace them when you see any of these:

• The foam has flattened and no longer springs back, so you feel the frame underneath.
• The fabric has faded from sun exposure or looks tired next to the rest of your patio.
• The covers are torn or stained beyond cleaning, even though the foam is fine.
• The cushions hold water or smell musty after rain, a sign the foam has broken down.

A new set of cushions on a solid frame reads as a whole new piece of furniture, at a fraction of the price of replacing it. For more on what deep seat cushions are and how they are built, see our guide on what a deep seat cushion is.

What you need to measure: six numbers

A deep seat cushion is really two cushions, a seat and a back, so a full measurement is six numbers:

How to measure a deep seat cushion, step by step

Use a firm tape measure, the metal carpenter kind, rather than a soft tailor tape. A soft tape sags and gives you numbers that are off by half an inch, which is enough to leave a gap or an overhang.

1. Seat width. Measure the seat frame side to side at its widest point, from the inside of one arm to the other.
2. Seat depth. Measure from the front edge of the seat straight back to where the back cushion will rest.
3. Seat thickness. Decide how deep you want to sit. Four inches is standard, five to six inches gives a plusher lounge feel.
4. Back width and height. Measure the back frame the same way, side to side and bottom to top.
5. Back thickness. Three to four inches is typical for a supportive back pillow.
6. Round to the nearest inch and write all six numbers down before you order.

The back pillow rests on top of the seat cushion, so its ordered height is the frame height minus the seat thickness. For a full step-by-step version with that back-height calculation worked out, see our deep seating measuring guide.

Measure the frame, not a flattened cushion

If your old cushion has gone flat or compressed at the edges, do not copy its dimensions. A cushion that has lost its shape measures smaller than it should, and if you order to those numbers the replacement will be too small. Measure the frame instead. The frame has not changed, so it gives you the true size the cushion needs to fill.

The one exception is thickness. The frame cannot tell you how thick you want the new cushion, so that is a comfort choice you make on top of the frame measurements.

Common deep seat sizes

Once you have your seat measurements, they usually land near one of these common sizes. If yours matches, these are ready to order in your fabric and thickness. If it does not, order a custom size cut to your exact numbers.

• 24 x 24, the standard deep seating size
• 22 x 24, for a slightly shallower seat
• 26 x 24, for wider seats
• 27 x 24, for extra deep frames

Choosing foam and fabric for the replacement

Two choices decide how long the new cushions last. For foam, high-resilience or high-density foam holds its shape under daily outdoor use, where cheap foam flattens again within a season. For fabric, a solution-dyed or performance outdoor fabric resists fading, water, and mildew, which is what killed the last set. Both are worth spending on, since the whole point of replacing is to not do it again in a year.

Custom vs universal replacement sets

Universal replacement sets come in a few fixed sizes and rarely match a specific frame, so you end up with a cushion that gaps at the back or hangs over the front. A custom deep seat cushion is cut to your six numbers, so it sits cleanly on the frame the way the original did. Since deep seating frames vary widely between brands, custom is the reliable way to get the fit right. Browse the full range in our deep seat cushions collection, or order a matching seat and back set in one go.

Measuring and replacing deep seat cushions FAQs

How do you measure deep seat cushions?
Measure six numbers: the seat width, depth, and thickness, plus the back width, height, and thickness. Use a firm tape measure, measure the frame rather than a flattened cushion, and round to the nearest inch.

Should I measure the old cushion or the frame?
Measure the frame. An old cushion that has flattened or compressed measures smaller than the true size, so copying it gives you a replacement that is too small. The frame gives the correct dimensions, except for thickness, which is your comfort choice.

When should I replace deep seat cushions?
Replace them when the foam has flattened and stopped springing back, the fabric has faded, the covers are torn or stained, or the cushions hold water and smell musty. If the frame is still solid, new cushions renew the whole set.

What size deep seat cushions do I need?
It depends on your frame, but most seats land near 24x24, 22x24, 26x24, or 27x24 inches. Measure your seat frame and order a custom size cut to your exact numbers if it does not match a standard size.