---
title: "How to measure a bay window seat cushion: every edge"
url: "https://cushionguide.com/answers/how-to-measure-bay-window-seat-cushion/"
section: "The Cutting Table"
author: "Nate Kowalski, The Pattern Engineer of Detroit"
author_url: "https://cushionguide.com/masters/nate/"
published: "2026-01-07"
updated: "2026-01-07"
keywords: "how to measure a bay window seat cushion, bay window cushion measurements, trapezoid window seat cushion, angled window seat cushion, custom bay window cushion"
---

# How do I measure a bay window seat for a cushion?

*A bay window seat is a polygon pretending to be a bench. Treat it as a list of straight lines, partner, and it gives up its secrets.*

Also asked as: It's a bay window, so how do I give measurements?; There are weird angles to my window seat.

> **The quick answer:** Measure a bay window seat by sketching it from above and writing every edge length on the drawing: the back edge against the window, the front edge, each angled side, and the depth from front to back. Type the numbers in your message as well, choose the size range by your longest edge and depth, and the workshop checks the geometry before cutting.

![Caramel bouclé trapezoid bay window cushion edged in cream piping on a cream paneled bench under arched windows](https://cushionguide.com/media/bay-window-cushions/caramel-trapezoid-bay-cushion-cream-piping-arched-1600.webp "Cream piping draws the long angled outline of this caramel bay cushion, making the custom shape clear at a glance.")

## Key facts

- Draw the bay seat from above and write every edge length on it, in order.
- On the trapezoid chart, E is the depth front to back; A is often the thickness.
- For bays with several windows, measure every line between the breaking points plus the depth at each point.
- Bay cushions follow the real angles; curved corners would leave gaps.
- Choose the size range by your longest edge and your depth, e.g. 105 in (267 cm) and 18 in (45.5 cm).
- Upload the drawing and a photo of the bay, and type each side length in the message too.
- Multi-angle bays can be one continuous cushion, with a zipped removable cover and firm foam.

## Five measurements, in order

1. **Sketch it from above**: Usually a trapezoid, sometimes more angles. A simple hand sketch is enough.
2. **Back edge, then front edge**: The back edge runs against the window; the front edge is where your knees go.
3. **Every angled side, edge by edge**: Straight lines at the corners, never a curve.
4. **Depth at every breaking point**: Front to back. With several windows, take it wherever the line breaks.
5. **Label and type**: Letter the sides A to E; type every number too.

## Why straight lines beat a pretty curve

Angles are just lengths in disguise. Give the workshop every edge and it rebuilds your bay on paper, checks that the shape closes, and confirms before anything is cut. On the trapezoid chart, E is the depth and A is often the thickness, so say which letter means what.

Size doesn't scare anyone: a bay 98.5 in (250 cm) across the front, 62.5 in (159 cm) at the back and 23 in (58 cm) deep became one continuous cushion.

Try your numbers in the [bay window calculator](https://cushionguide.com/studio/bay-window-calculator/) or read the [3-sided bay Pattern](https://cushionguide.com/guides/bay-window-seat-cushion-3-sided/); finished [bay window cushions](https://cushionguide.com/cushions/bay-window-cushions/) show the result.

> **Tailor's margin:** Measure a bay window seat edge by edge at the corners, never as a curve. Bay corners are angled, and a curved cushion leaves gaps.

> A bay window cushion 98.5 in across the front and 23 in deep can still be one continuous piece, as long as every edge is measured.
>
> — Nate

## Buyer questions

**A common question:** My bay seat has angled corners. Should the cushion curve there, or do I measure every edge?

**The workshop's answer:** Measure every edge. Bay corners are angled, so a curved cushion would leave gaps. Pick the size range by your longest edge and depth, and upload a drawing with every edge, plus thickness and fabric code.

**A common question:** My sketch is hard to read. How should I send bay window measurements?

**The workshop's answer:** Type every side length in the message as well as sending the sketch. One buyer using an angled-top bay style wrote A = 4.3, B = 4.3, C = 78.5, D = 48, E = 24, F = 24 and G = 23 in.

**A common question:** What if my walls aren't square and the numbers don't add up?

**The workshop's answer:** The workshop draws the cushion to scale and checks that it closes. If not, you'll be asked to re-measure, check both diagonals or fill in a lettered outline. A gap within 1/4 in is accepted, and nothing is cut until you confirm.

## Questions buyers ask next

### Which size do I pick on the trapezoid listing?

Pick the range that covers both your longest edge and your depth, for example 105 in (267 cm) and 18 in (45.5 cm), and upload the full drawing with the order.

### Can a bay with several windows be one cushion?

Yes. Multi-angle bays have been made as one continuous cushion. Measure every line between the breaking points and the depth at each, and the geometry is checked from your drawing first.

### Is the bay window cushion cover removable?

Yes. A zipped, removable cover over firm foam is standard on bay window cushions, whether the bay is a simple trapezoid or a multi-angle shape made in one continuous piece.

## Related at the atelier

- [Bay Window Cushion in Dusty Rose Linen, Cut to the Angle](https://cushionguide.com/readings/dusty-rose-bay-seat-cushion-dressing-room/): A bay window cushion starts with a drawing, not a fabric: mark every side length and both angled ends, and the quote comes back exact.
- [Bay Window Cushion for a Dog: Denim Blue, Cut to Every Facet](https://cushionguide.com/readings/denim-blue-bay-window-cushion-golden-retriever/): A bay window seat cushion feels generous when it is cut to the bay's own angles, edge to edge, instead of stopping square short of the returns.
- [Three-Piece Bay Window Cushion in Teal: Reading the Angled Joints](https://cushionguide.com/readings/teal-three-piece-bay-cushion-angled-joints-closeup/): A bay window cushion is usually made in three pieces: a center trapezoid and two angled wings that butt together on each corner of the bay.
- [Craftsman window seat cushions for shallow bays and short returns](https://cushionguide.com/concepts/craftsman-bungalow-window-seat-cushions/): A craftsman window seat cushion is usually a clipped trapezoid: a long front edge, a shorter back edge, and a short straight return at each end before the angled sides begin.
- [Big bays, long seats: where to split a large bay window cushion](https://cushionguide.com/concepts/large-bay-window-cushions/): A large bay window cushion longer than about 7.5 ft (2.3 m) is usually best made in two or more pieces, joined at a bay corner or at the midpoint.
- [Bay window seats in Victorian houses, one cushion at a time](https://cushionguide.com/concepts/victorian-bay-window-seat-cushions/): A Victorian bay window seat cushion is a custom trapezoid, cut from a drawing that shows every edge, the straight depth and, in an old house, both diagonals.
- [How to measure a trapezoid cushion so the numbers close](https://cushionguide.com/guides/trapezoid-cushion-measurements/)
- [Measuring a 3-sided bay window seat cushion, panel by panel](https://cushionguide.com/guides/bay-window-seat-cushion-3-sided/)

*± 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/answers/how-to-measure-bay-window-seat-cushion/