Foam & Cushions · How-To Guide

How to Measure Couch Cushions for Replacement Foam

A few careful measurements are the difference between foam that fills your cushions and foam that fights them.

Mike Handelsman

CEO, FoamOrder8 min read

A replacement cushion only fits when the new foam matches the cover it goes into, not the worn-out foam you're taking out. Measure accurately and a tired sofa comes back to life. Measure the wrong thing and even the right foam will bulge, wrinkle, or sit too flat.

Measuring is simple once you know what to record and what to leave out. Below is the quick method for standard cushions, followed by what changes for feather-filled, T-shaped, and made-to-pattern shapes.

01 · The short answer

Measure the cover, not the old foam.

Measuring cushion thickness seam to seam with a tape measure — Measure the cover seam to seam. The worn foam inside has already lost its shape.

1Take the cover off and lay it flat.

2Measure length, width, and thickness seam to seam, or between the piping if your cover has it.

3Calculate your final dimensions using the foam allowance rule below.

4Pick your cushion shape and enter your numbers.

The golden rule of foam allowance

Ordering bare foam (without dacron)? Add a small allowance to your seam-to-seam cover measurements so it fills out snugly:

·Standard cushions (4″ or thicker): add ½″ to your measurements.

·Thin cushions (1″ to 3″, like chair pads): add ¼″ to your measurements.

Adding a Dacron wrap? Order the foam at the exact seam-to-seam cover size. The wrap plumps up the rest and builds the crown.

Not sure which applies? Contact us.

Simple box cushion

Measure Length × Width × Thickness, add your allowance, done.

Feather-filled

Needs unique adjustments. See the feather-filled section before you measure.

T-shaped or curved

Capture the extra dimensions or send a pattern.

Interactive quiz

Not sure how your cushion should be measured?

There are real nuances to measuring, depending on your situation and the cushion you have now. That's why we built this quick interactive quiz. It gives you a short-answer version in a few taps, but we still recommend reading the whole guide to really understand what's going on.

02 · Before you even start

Start by avoiding these mistakes

Before you even pick up the tape measure, know these. Almost every bad-fitting cushion comes from one of them, and catching it now saves you a reorder later.

Measuring the old foam

Worn foam shrinks, sags, and loses its shape, so it reads smaller than the cushion was meant to be.

Instead: measure the fabric cover seam to seam.

Measuring the cover with the foam still inside

With foam still in the cover, the fabric stretches over the cushion's crown and your numbers come out too big.

Instead: unzip the cover, take the old foam out, and lay the cover flat before measuring.

Treating a feather cushion like a foam one

Feather envelopes measure much larger than the foam that belongs inside them.

Instead: follow the feather-filled section, which needs its own adjustments.

Skipping the "plump" allowance

Foam cut to the exact size of a stretched cover can look baggy.

Instead: add about half an inch, or add a Dacron wrap, for a full, crisp fit.

Not sure about your cushion? We are happy to help you measure it right.

(415) 503-9314 Book a 1-on-1 design consultation

Customer service is available 7AM–5PM PST. Prefer to talk it through? Book a free one-on-one design or help call at a time that works for you, or contact us any time.

03 · Tools & prep

What you'll need

Measuring takes about five minutes. Gather these first.

Tape measure

A flexible tape follows the cushion's shape best.

Pen and paper

For sketching the shape and noting each number.

The cushion cover

Work from the cover with the old foam removed.

We accept measurements in inches or centimeters, so use whichever is easier for you.

04 · The method

How to measure couch cushions, step by step

Four steps take you from cover to cut size.

Custom replacement foam cushions in a range of shapes and sizes made by FoamOrder

1

Remove the cover and lay it flat

Unzip the cover, take out the old foam, and lay the cover flat on a hard surface with the zipper facing away from you. Smooth out any wrinkles, but don't stretch the fabric. You want the cover sitting at its true size.

Measuring the cover rather than the old foam is the single most important step. Old foam compresses, sags, and loses its shape over the years, so it reads smaller than the cushion was ever meant to be.

2

Sketch and label the shape

Draw the cushion on paper and label each side as you go. This keeps things clear for anything beyond a plain square, like T-cushions, L-cushions, and trapezoid seats, and keeps a multi-cushion order from getting mixed up.

3

Measure length, width, and thickness

Measure seam to seam, or between the piping if your cover has it. Take the length from back to front, the width from side to side, and the thickness from a side or back border panel where the fabric is least stretched or worn. Record all three on your sketch.

Measure at the seams, not over the middle. The center of a cushion rises into a crown, so a measurement taken across the top reads too big. Measure twice to be sure your numbers match.

4

Apply the foam allowance rule

Now apply the Golden Rule of Foam Allowance from Section 01 to your final numbers. If you're ordering bare foam, add ½″ for standard deep cushions (4″ or thicker) or ¼″ for thin cushions (1″ to 3″). This ensures the foam fits snugly without over-stretching or distorting a thinner cover.

If you're adding a Dacron wrap, keep your foam order at the exact seam-to-seam size. The wrap fills out the cover and builds that beautiful, rounded crown over the foam core.

Still deciding? Contact us with your numbers and we'll confirm the exact cut.

05 · Before you order

Check inside the cushion first

Unzip the cover and look at how the cushion was actually built. Two minutes here is what stands between a perfect fit and a disappointing one. Here's exactly what to look for:

Cross-section of a couch cushion showing the foam core wrapped in Dacron batting inside the cover

01

Compare the foam to the boxing

Measuring the cover seam to seam is still your main method. This is just an optional sanity-check for the thickness: because the foam and the boxing were sometimes built at different heights, a quick look inside confirms your cover measurement matches how the cushion was actually made.

The boxing, sometimes called the border, is the side panel of the cover that sets its height. Check whether the foam inside actually matches that border height, because the two are not always the same.

One caution: worn foam naturally shrinks and sags with age, so a core that now sits shorter than the boxing is usually just degraded, not built that way. Only match a thinner or thicker core if the difference is clearly deliberate design, like a thick down-wrap or a pronounced knife-edge, rather than ordinary wear.

TERM Boxing: the cover's side panel; it sets the finished height.

02

COMMON MISTAKE

Don't measure the Dacron wrap

Most cushions have a layer of soft polyester batting, usually called Dacron, wrapped around the foam. It's a filler that softens the edges and adds roundness, and it typically runs about ¾″ to 1″ thick. Never include it in your foam measurement.

If your wrap is thicker than usual (some run 1¼″ to 1½″), order a matching wrap so the finished cushion sits the same. You can often peel the existing wrap off and reuse it.

TYPICAL WRAP ½″ – 1″

HEAVY WRAP 1″ – 1½″

03

Understand the crown

The crown is the gentle rise in the center of a finished cushion. It doesn't come from thicker foam. It comes from the Dacron wrap or filled envelope sitting over the foam while the border pulls the sides down. That's exactly why you measure at the seams and let the wrap create the loft.

CROSS-SECTION · HOW A CROWN FORMS side view

Worked example. A 4″ foam core gets an equal heavy 1½″ Dacron wrap top and bottom, which crowns the cushion on both faces. The finished cushion reads around 7″ of loft through the middle while the border stays near 4″. You order the 4″ foam, not the 7″ you'd measure across the crown.

04

WATCH OUT · HIGHER-END PIECES

Watch for feather-filled cushions

Higher-end furniture often wraps the foam core inside a separate feather or down envelope. Because these covers were built to crown, or bulge elegantly, from the soft fill, the outer cover is cut larger than the foam sitting inside it. How you measure depends entirely on whether you're keeping your current envelope or replacing it.

PATH 1

If you're keeping the feather envelope

You're only replacing the tired foam core inside the feathers. The goal is a core that fills the envelope exactly, so the feathers can plump it into that beautiful crowned shape.

Width & depth

Pull the outer cover taut and measure seam to seam. Order the foam with a ¼″ allowance so the core fills the cushion's cover corner to corner, snug against every edge.

Thickness

Measure the outer cover's side border (the boxing) seam to seam and order the foam at exactly that thickness. No subtraction, no allowance. A completely filled feather envelope is what creates the beautiful crowning effect.

EXAMPLE

A cover that measures 5″ thick seam to seam takes a 5″ foam core. Get the measurement right and the math takes care of itself.

PATH 2

If you need to replace the feather wrap (or want an alternative)

Your cover was built for crowning, so replacing the insert with a bare foam block, or foam in a thin Dacron wrap, will leave you with a baggy cushion. We recommend keeping your feather envelope whenever you can. But if yours has to go (stains, moisture damage, or it's simply worn out), you have two primary options:

1

Order a new envelope from FoamOrder. You can order just a down envelope without a foam core, or order a foam core wrapped in a down envelope as one complete cushion.

2

Fake it till you make it. Down feather envelopes are not a budget-friendly option, and this is where you can get creative. A full or double Dacron book wrap is the minimum. Better yet, call customer service and have them triple or even quadruple wrap your cushion in Dacron to recreate the crowning effect.

Contact us about your cushion

06 · Shapes

Measuring by cushion shape

Couches use more than plain squares. Find your shape below, measure the way it describes, then pick that shape when you order.

See it in 3D first

Enter your measurements and a live 3D model renders your exact cushion, so you can check the fit before anything is cut.

Price every foam

Get an instant quote across our foam types and firmness levels, so you can weigh comfort against budget before you buy.

Square & rectangle

Measure length, width, and thickness seam to seam. If the cover has piping, measure between the piping.

Measure square & rectangle→

T-cushion

Measure the wider front where it flares around the arm and the narrower back as two separate widths, plus length and thickness.

Measure T-cushion→

Curved T-cushion

A T-cushion with a curved front. Take the front and back widths and the length, then trace the curved edge onto paper.

Measure curved T-cushion→

L-cushion

Measure each leg of the L on its own. Sketch the shape and label every side so nothing gets flipped.

Measure L-cushion→

Curved L-cushion

Measure each leg of the L, then trace the curved edge so the radius comes out right.

Measure curved L-cushion→

Trapezoid & window seat

Measure the front width, the back width, and the depth front to back. Common for window seats and chair pads.

Measure trapezoid seat→

Round

Measure the diameter across the widest point and the thickness.

Measure round→

Bolster

For a cylindrical bolster, measure the diameter of the end and the overall length.

Measure bolster→

Curved front

Measure it like a rectangle to the seams first, then mark the curve, or trace the curved edge onto paper.

Measure curved front→

Custom or complex shapes

Trace the cushion onto paper, follow the seam all the way around, and send us the pattern. We cut to it exactly.

Send us your pattern→

The bottom line

Measuring a cushion comes down to one habit: measure the cover seam to seam, not the tired foam inside it. From there, the details take care of the rest. Let the Dacron wrap build the crown, keep the feather envelopes and refill them, and account for your cushion's real shape when you order. When in doubt, over-measure by a hair rather than under.

Do that, and the cushion you get back will look and sit the way it did the day the sofa was new. If your situation does not fit neatly into any of these, that is exactly what we are here for. Send us your measurements or a photo and we will help you get it right the first time.

Start your custom couch cushion→

Written by

Mike Handelsman

Owner & President, FoamOrder

Mike leads the family of foam and upholstery brands behind FoamOrder.com and Upholster.com, which have served consumer and commercial customers for over 20 years. A graduate of Duke University and Harvard Business School, he works directly on helping customers get the exact foam and cushions they need.