---
title: "Bench Cushion Thickness: Work Back From an 18 in Seat"
url: "https://cushionguide.com/guides/cushion-thickness-seat-height-calculator/"
section: "The Pattern Room"
author: "Nate Kowalski, The Pattern Engineer of Detroit"
author_url: "https://cushionguide.com/masters/nate/"
published: "2026-02-19"
updated: "2026-09-24"
keywords: "bench cushion thickness, cushion thickness for seat height, how much does foam compress, 2 vs 3 vs 4 inch cushion, window seat height with cushion"
---

# How thick should a bench cushion be? Work back from seat height

*Most thickness regrets start with a number picked before anyone measured the bench. Flip the order, partner: seat height first, thickness last. It's one subtraction, and I'll show my work.*

> **The quick answer:** Subtract your bench height from the seat height you want, and the difference is your cushion thickness. For dining, aim for about 18 in (46 cm) finished, within 17 to 19 in, so a 15 in bench takes a 3 in cushion. Standard options are 2, 3, 4 and 5 in, and 4 in (10 cm) is the usual default.

![Thick mustard bouclé box cushion on a walnut sled-leg bench with cream and sage pillows beside a tall city window](https://cushionguide.com/media/bench-cushions/thick-mustard-boucle-cushion-walnut-sled-bench-1600.webp "A thick mustard bouclé cushion gives a low walnut sled bench real comfort, styled with sage and cream pillows.")

## The formula, before the foam

Here's the whole method in one line: **platform height + cushion thickness = finished [seat height](https://cushionguide.com/glossary/#seat-height)**. Bench cushion thickness is the last number you choose, not the first.

Measure the platform, decide the seat height you want, subtract. For a dining bench the target is about 18 in (46 cm), inside a 17 to 19 in (43 to 48 cm) band. A buyer in the US had a 17 x 35.75 in mudroom niche standing 15 in high and wanted an 18 in seat. 18 − 15 = 3. A 3 in (7.5 cm) cushion, done.

Foam does settle a little under a sitter; a 3 in cushion may ride about 2 1/2 in under you. The workshop's standard foam is a firm high-density about 2.0 lb/ft³ (32 kg/m³), so design to the full thickness and treat the settle as bonus knee room. The glossary explains [compressed height](https://cushionguide.com/glossary/#compressed-height) and [table clearance](https://cushionguide.com/glossary/#table-clearance).

## Let the Studio do the subtraction

The [seat height calculator](https://cushionguide.com/studio/seat-height-calculator/) takes your bench height, your table height and your own height, and returns the thickness that keeps your feet on the floor and your knees under the table, drawn to scale. Run it once with your real numbers and once with the thickness you were planning to buy. If the two disagree, believe the tape.

Working on a window seat instead of a table? Same sum. The ceiling is just different: the sill, the sash or whatever hangs above the seat. What's above yours?

## Where 2, 3, 4 and 5 in put you

| Cushion | 15 in bench | 16 in bench | 17 in bench | Best for |
|---|---|---|---|---|
| 2 in (5 cm) | 17 in (43 cm) | 18 in (46 cm) | 19 in (48 cm) | High platforms, benches beside a table, tight sills |
| 3 in (7.5 cm) | 18 in (46 cm) | 19 in (48 cm) | 20 in (51 cm) | Most kitchen nooks and window seats; the neat middle ground |
| 4 in (10 cm) | 19 in (48 cm) | 20 in (51 cm) | 21 in (53 cm) | The standard: everyday seating, low platforms, napping on hard wood or wicker |
| 5 in (12.5 cm) | 20 in (51 cm) | 21 in (53 cm) | 22 in (56 cm) | A fuller look; sits like 4 in and can look heavy on a small bench |

Finished seat heights at full, uncompressed thickness. Under a sitter, a 3 in cushion may ride about 2 1/2 in.

## Seven measured moves to the right thickness

1. **Measure the platform**: Floor to the surface the cushion will sit on, at the front edge where your knees go. Read it to the nearest 1/8 in, then measure again. Measure twice; the fabric remembers. If a carpenter is still building the bench, wait for the finished piece.
2. **Choose the seat height you want**: At a dining table, aim for about 18 in (46 cm), within 17 to 19 in. Easier still, measure a chair you already like, floor to the top of its seat. A window seat meant for perching can sit a little higher; a lounging nook can sit lower.
3. **Subtract**: Target seat height minus platform height is your thickness. An 18 in target over a 15 in bench gives 3 in (7.5 cm).
4. **Round to a standard thickness**: The standard options are 2, 3, 4 and 5 in (5, 7.5, 10 and 12.5 cm), and within that range thickness doesn't change the price. In-between values such as 2.5 or 4.5 in go in the personalization box. Thicker than 5 in is quoted individually.
5. **Check the table and the window**: Keep 10 to 12 in (25 to 30 cm) from the cushion top to the tabletop. Knee room is a separate check: floor to the apron or lowest rail, minus seat height, then sit on towels stacked to that height. On a window seat, check the sill, an opening sash and anything like an AC unit above the seat.
6. **Mock it up before you order**: Stack books or a folded blanket to the thickness you picked and sit through a whole meal. Feet flat and knees clear means you're done. It costs nothing, and it beats any spreadsheet.
7. **Write the thickness on the order**: Put the exact thickness for every piece in the order's personalization box, not only in a chat message; production reads the order. When a vacuum-packed cushion arrives, give it 3 to 4 days to reach full size before you measure.

## Two sills and an air conditioner

A parent in the US was fitting window-sill cushions for a daughter's apartment. She ordered fabric samples first, chose her fabric and a light blue pairing from them, and even sent a photo of the rug so the workshop could confirm the match.

The two sills were different sizes, so two different cushions. The deciding number wasn't comfort at all. One sill sat below an air-conditioning unit, and that unit capped the height. She kept both cushions at 2 in (5 cm), so the pair matched and the low one cleared.

That is the same sum run backwards from an obstacle instead of a table. Find the thing above the seat first, then choose the foam.

## Why 4 in and 5 in feel the same

Every standard thickness uses the same firm 32-density foam wrapped in polyester fiber. So 4 in and 5 in sit the same; they differ only in looks. On a 25.5 x 71 in (65 x 180 cm) bench, 4 in already reads plush and sofa-like, and 5 in can look heavy. 3 in is the middle ground for benches and window seats.

The base matters too. Over a plywood kitchen-nook bench, 3 in is enough. On hard wood or wicker you'll nap on, like a daybed or a swing platform, the workshop recommends 4 in. Want more loft? 6 or 8 in can be quoted at a higher price.

Most buyers land on 3 or 4 in. One more number for your notebook: listings state that a handmade cushion can finish about 1 in either way, so don't design a window seat to the last sixteenth. Related patterns: [window seat cushion thickness](https://cushionguide.com/guides/window-seat-cushion-thickness/) and [banquette cushion thickness](https://cushionguide.com/guides/banquette-cushion-thickness-table-height/); shapes and sizes live under [bench cushions](https://cushionguide.com/cushions/bench-cushions/) and [window seat cushions](https://cushionguide.com/cushions/window-seat-cushions/).

## Common mistakes: the cushion that sat too high

- ✗ Choosing thickness for comfort before measuring the seat against the table or sill. It comes up again and again, and the usual fix was a new, thinner cushion.
- ✗ Putting 4 in on a high bench. It lifts the sitter too far; on high benches consider 2 to 3 in.
- ✗ Forcing a thick cushion into a frame. It buckles instead of sitting flat.
- ✗ Forgetting what's above the seat: the sill, an opening window, an AC unit.
- ✗ Measuring a bench the carpenter hasn't finished.
- ✗ Confirming the thickness in chat only. One buyer agreed 4 in by message and the reorder arrived 2 in, because production followed the order.
- ✗ Measuring a vacuum-packed cushion on day one. Foam needs 36 to 72 hours to inflate and 3 to 4 days to reach full size.

> **Tailor's margin:** Bench height plus cushion thickness equals seat height: a 15 in bench with a 3 in cushion lands at 18 in, right at dining height.

> A bench cushion that's too thick steals knee room. Keep 10 to 12 in between the cushion top and the tabletop, and pick the thickness last.
>
> — Nate Kowalski

## Buyer questions: thickness and height questions

**A common question:** How thick should my cushion be to get a certain seat height?

**The workshop's answer:** Final seat height is the bench height plus the cushion thickness. A 17 x 35.75 in mudroom niche standing 15 in high takes a 3 in cushion for an 18 in seat: choose the nearest options (17 in, 36 in, 3 in) and write the exact 17 x 35.75 x 3 in in the note. If you ask for a seat height such as 26 in, the workshop checks whether you mean floor to top of seat and asks for width, length and height.

**A common question:** What's the real difference between a 2, 3, 4 and 5 inch cushion?

**The workshop's answer:** 2 in is a slim, low-profile pad; 3 in adds cushioning and a fuller look while still sitting neatly; 4 in is noticeably plumper; 5 in is the deepest standard option. All use the same firm 32-density foam wrapped in polyester fiber, so 4 and 5 in feel the same and differ only in looks. On a 25.5 x 71 in (65 x 180 cm) bench, 4 in already looks plush and 5 in can look heavy.

**A common question:** What thickness do most people choose?

**The workshop's answer:** Most buyers choose 3 or 4 in. 4 in (10 cm) is the standard and the workshop's pick for everyday seating and a tailored built-in window seat; 3 in (7.5 cm) gives a trimmer profile and suits tight spots, like a 15 in (38 cm) gap under a windowsill. The foam is firm 32-density, so even 2 to 2.5 in stays supportive in a dining nook. The standard options cost the same, so choose on looks and fit.

**A common question:** Does a thicker cushion cost more, and a thinner one less?

**The workshop's answer:** Within the standard range, no: 2, 3, 4 and 5 in cost the same, because thickness isn't a big cost factor at regular sizes. Beyond that, foam volume drives the price and extra-thick cushions are quoted individually. On real quotes, going from 4 to 8 in added about half, while a single step such as 5 to 6 in added only a little.

**A common question:** Can my cushion be thinner or thicker than the standard 4 inches?

**The workshop's answer:** Yes, thickness is fully custom. Real orders have gone thinner, at 2, 3 and 3.5 in, and thicker, at 5, 6, 8 and 9 in, with floor cushions at 6, 8 and 10 in (15, 20 and 25 cm). Select the nearest option and write the exact thickness in the personalization box. Thinner usually costs the same as standard; thicker foam raises the quote.

**A common question:** How close to my ordered size will a handmade cushion be?

**The workshop's answer:** Listings state the finished size can vary by about 1 in either way, so a 5 in height can come out anywhere from 4 to 6 in, and long cushions are most affected. If a size is a hard maximum, say so: one buyer's absolute 24 in limit became a 23 in cushion. Measure height only once the cushion has fully expanded, and expect the edges to relax slightly with use.

## Seat height and thickness, answered

### How much does a foam cushion compress when you sit on it?

Less than most people guess with firm foam. A 3 in cushion may ride about 2 1/2 in under a sitter. With firm high-density foam, plan the look and the table clearance on the full thickness and treat the settle as a little extra knee room.

### What seat height suits a dining bench?

About 18 in (46 cm) from the floor to the top of the cushion, within a 17 to 19 in band. Check it against the table too: 10 to 12 in from the cushion top to the tabletop. Then check knee room: floor to the apron, minus seat height, and a test sit on stacked towels.

### How thick should a window seat cushion be?

Most window seats take 3 or 4 in. 3 in gives a trimmer profile, and 4 in gives the tailored built-in look. Where a sill, an opening sash or an AC unit caps the height, 2 in keeps the profile low and still sits comfortably on firm foam.

### How deep should the seat of a cushioned bench be?

For upright dining, 16 to 18 in of seat depth; banquettes run 18 to 22 in including the cushion, and lounge-style seats 22 to 24 in. Avoid going under 16 in, and remember that a back cushion takes about 3 in off the usable depth.

### When can I measure the thickness of a new vacuum-packed cushion?

Give it time. The foam takes 36 to 72 hours to fully inflate and 3 to 4 days to reach its ordered dimensions. Unpack it within a few days of delivery, lay it flat, and measure across the flat middle with the tape held square.

### Is a thicker cushion always more comfortable?

Not past a point. With the same firm foam, a 4 in and a 5 in cushion feel almost alike; the extra inch mostly changes the look and lifts you higher. Comfort comes from a seat height near 18 in, foam that doesn't bottom out and enough depth. If you want a softer sit, ask for softer foam or an extra wadding layer rather than more height.

### My built-in bench is 26 in deep. Should the cushion be 4 or 6 in?

Let the seat height decide first: bare bench plus cushion should land near 18 to 20 in. On a deep bench you lounge on, 6 in can make sense, and some guides keep 5 to 7 in for deep, low seats only. Remember that back pillows take roughly 4 in of depth, so a 26 in seat sits closer to 22 in once they're in.

## Related at the atelier

- [What cushion thickness do most people choose?](https://cushionguide.com/answers/most-popular-seat-cushion-thickness/): Most buyers choose a 3 or 4 in seat cushion, and 4 in (10 cm) is the standard for everyday seating.
- [What's the difference between a 2, 3, 4 and 5 inch cushion?](https://cushionguide.com/answers/2-vs-3-vs-4-inch-cushion-difference/): The difference between a 2, 3, 4 and 5 inch cushion is mostly the look: 2 in is a slim pad, 3 in a neat middle ground, 4 in noticeably plumper and 5 in the deepest standard option.
- [Cushion measurements explained: length, depth, thickness and units](https://cushionguide.com/guides/cushion-measurements-length-depth-thickness/): Every cushion size is three numbers: length (A), measured side to side along the front; depth (D), from the front edge back to the wall; and thickness (T), how tall the cushion stands.
- [One long cushion or two? Splitting a long bench or window seat](https://cushionguide.com/guides/long-bench-cushion-one-piece-or-two/): A long bench cushion is usually best split into equal pieces once the run passes about 79 to 90 in (200 to 230 cm).
- [One printable cushion measuring worksheet for any shape you order](https://cushionguide.com/guides/printable-cushion-measuring-worksheet/): A cushion measuring worksheet records one shape per sheet: length (A), depth (D) and thickness (T) for a rectangle; front, back, straight depth, both slants and both diagonals for a trapezoid; each…
- [Custom Bench Cushion Thickness: Working Back From Seat Height](https://cushionguide.com/readings/cream-mudcloth-style-cushion-dark-wood-storage-box/): Choose bench cushion thickness by working back from seat height: box height plus cushion thickness should land near 18 in (46 cm), inside the usual 17 to 19 in range.
- [Getting a custom cushion quote: what to send so it's right the first time](https://cushionguide.com/guides/custom-cushion-quote-what-to-send/)

*± 1/4 in — Nate*

---

Written by Nate Kowalski (https://cushionguide.com/masters/nate/) for CushionGuide (https://cushionguide.com/about/). The site explains made-to-measure cushions and the partner workshop makes them; measurements are in inches first. This Markdown mirrors the page at https://cushionguide.com/guides/cushion-thickness-seat-height-calculator/