How to Measure Your Sofa for a Cushion Support Board

The rule that matters more than the numbers

Take the cushions out and measure the bare seat base underneath them.

Cushions hang over the frame they sit on, usually by an inch or two all round. That's what gives a sofa its soft edges. The seat base is the surface the board actually rests on, so the seat base is the measurement that matches you to the right size.

Get this one right and everything else on this page is straightforward.

What you need

A tape measure. That's the whole list. Two minutes if you take your time.

Measurement one: inner width

Get every seat cushion out. Put the tape against the inside face of one armrest and run it straight across to the inside face of the other.

Inside, not over the top. You want the width of the space your cushions actually sit in, not the width of the sofa.

If your arms flare or curve, take the measurement down at seat-base level, because that's where a board is going to sit.

Measurement two: seat depth

From the front edge of the seat base, straight back to where the backrest starts.

Keep the tape square to the front edge. Angle it even slightly and you'll read long, so square is what gives you the number that matches your seat.

If your back cushions are loose rather than fixed, pull those out too and measure to the actual frame.

Sectional? One more number

Measure the main run and the chaise separately, same way both times. Inside faces, cushions out. You'll finish with the main run's width, the chaise's length, and one depth.

Sectionals vary far more than sofas do, which is why we'd rather look at yours than have you guess.

Rounding

Round to the nearest half inch. If a number lands awkwardly between, round down, on both width and depth.

A board sitting a little inside the space is exactly where you want it: fully on the seat base, hidden under your cushions, spreading your weight evenly across the whole seat. So when in doubt, err small.

Five things worth checking twice

• Measuring the cushions. The big one. Get them out and measure what was underneath.
• Measuring the outside of the sofa. That's its footprint in the room, not its seating area.
• Measuring over the arms. Adds several inches. Inside faces only.
• Angling the tape on depth. Keep it square to the front edge.
• Rounding up. When in doubt, round down.

Then what

Put your two numbers into the size finder and it'll tell you which board fits, with the fit range shown before anything goes anywhere near your cart. If your measurements land somewhere we don't build, it says so instead of rounding you to the nearest thing.

Or send them to us and a person will check them. Costs you nothing and it takes one look.