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The Cutting Table · a question, worked through

How thin can a window seat cushion be so the window still opens?

Rain doesn't negotiate, and neither does a window sash. Start with the gap under the frame and work down from there.

Answered by

The Weather Man of Casco Bay · · Updated

Pinned by Callum

The quick answer

A window seat cushion can be made as thin as 3/4 in (2 cm), but 2 in (5 cm) is the thinnest recommended for sitting. For most low-profile window seats, 2 to 3 in (5 to 7.5 cm) works. Measure the clearance under the window frame, give your absolute maximum height with the cover on, and the thickness is confirmed with you before production.

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Key facts

  • 2 to 3 in (5 to 7.5 cm) is the suggested thickness for a low-profile window seat.
  • Cushions of exactly 2 in (5 cm) have been made so the window above can still close.
  • 3/4 in (2 cm) and 1 in (2.5 cm) cushions can be made to order.
  • 1 in (2.5 cm) is considered too thin for seating; the recommended minimum is 2 in (5 cm).
  • At slim thicknesses the foam must be cut evenly and sized to the cover, or the cushion bulges above the limit.
  • Give your maximum height including the cover; the thickness is confirmed before production.

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Have Callum’s workshop cut this for you

Short list: size, sun hours, how fast it has to dry. The workshop goes through it with you. — Callum

Leave your details and the workshop will call you to confirm measurements, fabric, foam and piping. No prices, dates or payment on this page: it is a request, not an order.

Fabric · Foam · Pipingwhat the workshop will confirm with you

Fabric
The cover cloth: weave, color and care code.
Foam
At slim thicknesses the foam must be cut evenly and sized to the cover, or the cushion…
Piping
The corded seam edge: matching, contrast or none.
Only for this request: no marketing calls or texts. Outside the US, add the country code.
In inches: length × depth × thickness, plus any angles or cut corners.

* Required. A member of the workshop team will call you to talk it through; nothing is charged and nothing is made until you have agreed on every detail with them.

We use these details only to answer this request and make your cushion: your name and contact details, the cushion details and photos you send, the page you came from and the ad or link that brought you, if any. The workshop that makes the cushions receives them. We don't sell them or share them for advertising, and we delete requests after 24 months. Privacy notice for requests.

Nothing is made or charged until you approve the details.

Want to pick the shape and add photos? Use the full quote form

Measure the sash, then the seat

Most window seats have room to spare. The ones that don't are the ones that write in: a sash swings down or a casement swings in, and a cushion a hair too tall stops it cold.

So the workshop suggests 2 or 3 in (5 or 7.5 cm) for a low-profile window seat cushion. Thinner is possible: 3/4 in (2 cm) and 1 in (2.5 cm) are made to order. But at 1 in you're sitting on a pad, and it may not give adequate support. That's why 2 in (5 cm) is the recommended minimum.

The window seat thickness Pattern walks through the trade-offs. What's the gap between your seat board and the bottom of the frame, friend?

Finding the number the cushion can't pass

  1. Close the window fully

    Measure straight down from the lowest point of the frame or sash to the seat board. That is your clearance.

  2. Check it in two or three spots

    Old seats and sills are rarely level. Use the smallest reading.

  3. State it as a maximum, cover included

    Write the absolute top height with the cover on, not the foam alone. The thickness glossary entry explains why the two differ.

  4. Confirm before cutting

    The workshop confirms the final thickness with you before production. The window seat measuring Pattern covers length and depth.

A real project

A trapezoid seat that needed to drop an inch

A buyer wrote in about a trapezoid window seat. The listing's thicknesses started at 3 in (7.5 cm), and that was already too tall for the window. The shop switched on a 2 in (5 cm) option for the order. The buyer asked about 1 in (2.5 cm) too; the honest answer was that it can be made, but it's extremely thin to sit on. They took the 2 in, and the window still closes.

A window seat cushion can go as thin as 3/4 in (2 cm), but 2 in (5 cm) is the thinnest that still sits like a seat.

Callum
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Buyer questions

  1. A common question

    How slim can you make a window seat cushion? Would 2 in or even 1 in fit under my sill?

    The workshop's answer

    2 in (5 cm) is available; on one trapezoid listing that normally starts at 3 in (7.5 cm), a 2 in option was switched on for the order. 1 in (2.5 cm) can be made, but it is extremely thin for sitting and may not give adequate support, so at least 2 in is recommended.

  2. A common question

    Can you make a 3/4 in window seat cushion so the window can still open?

    The workshop's answer

    Yes, 3/4 in (2 cm) cushions are made to order; one pair measured about 68 x 21 in (172.5 x 54 cm) and 51 x 21 in (130 x 53 cm). At that thickness the foam must be cut evenly and sized to the cover, or it bulges past your limit, so state your absolute maximum including the cover.

  3. A common question

    Could you make a windowsill cushion exactly 2 in high?

    The workshop's answer

    Yes. A windowsill cushion was made at exactly 2 in (5 cm) so the window above could still close.

  4. A common question

    How thick should a window seat cushion be if I don't want it covering the window?

    The workshop's answer

    For a narrow window seat, 2 or 3 in (5 or 7.5 cm). The final thickness is confirmed with you before production, so measure the height under the window frame first.

Questions buyers ask next

Can a 1 in window seat pad still have piping?

Piping works on cushions down to about 1 1/4 in (3 cm). Pads of 1 in (2.5 cm) and 3/4 in (2 cm) are made without piping, so plan on a plain edge if you need the slimmest possible profile under the sill.

Why does a slim cushion look flat when it first comes out of the box?

Compressed foam can take up to a week to fully expand. Take the cover off, shake and stretch the foam, and give it several days. If a piece is still flat after that, send photos.

Is 2 in thick enough for everyday sitting on a window seat?

It is the recommended minimum for seating, and exact 2 in (5 cm) cushions are made for windows that need the clearance. If your sash allows 3 in (7.5 cm), you get a little more cushion.