Measuring for Bay Windows Blinds

Measuring Venetian Blinds for Bay windows can, at first, appear daunting. So we sat down with our Venetian Blind experts to draw up this guide, which is simple and easy to follow.

The first step is to determine the ‘depth’ of your Venetian blind. This is the distance that the blind will hang away from the window itself. The depth is determined by the size of the slat, just see our handy guide below.

All blinds for bay windows should be ordered as exact size.

Depth Guide

Slat size (mm) Depth (mm)
25 & 27 60
35 60
50 80

Easy peasy.

We do also have to account for anything sticking out of the window, such as a handle. But all you have to do is add the depth of the handle to the table above.

For example

If you are ordering a Venetian blind with 35mm slats and have a 30 mm handle, it would look like this.

35mm slat = 60mm depth.
60mm depth + 30mm handle = 90mm.

Your depth, for all further instructions is 90mm.

There are 4 different ways you can structure Bay Windows with Venetian Blinds, each with their own merits and measuring guides. But never fear, just follow the simple instructions below and you’ll have stunning, perfectly fitted Venetian blinds in no time. For all the below examples, we will assume the front window is 100cm wide, with the recess being 50cm deep and the slats are 35mm.

Type A - For square bay windows – front blinds full width

Type A - For square bay windows – front blinds full width

In this style the Front Venetian Blind covers the entire front window, with the Side Venetian Blinds flush against it. With this style the front window gets the most coverage. This is the best style if you want to stop direct light from the front. It also offers the highest level of privacy from directly in front of the window. There may be a small gap where the side blinds meet the front blinds but this is usually obscured by the window frame at the corners.

Guide for Front Venetian Blind

Measure the width of the recess where the front blind will go. Make sure you take the smallest measurement if the recess or frame varies from top to bottom. Then deduct 1.5 cm for clearance.

Front bay window recess width 100cm.

Deduct 1.5cm for clearance 100cm - 1.5cm = 98.5cm.
You should order the front blind at 98.5cm.

Guide for Side Venetian Blinds

Measure the width of the recess where the side blind will go. Make sure you take the smallest measurement if the recess or frame varies from top to bottom. Deduct the depth in cm according to the slat size of the front blind (see depth chart). This is to account for the front venetian blind. Then deduct 1.5 cm for clearance. Repeat this for the other side bay window blind.

Side bay window recess width 50cm.

Deduct depth for 35mm slats (60mm, to account for the front blind) 50cm – 60mm = 44cm.
Then deduct another 1.5cm for clearance 44cm – 1.5cm = 42.5cm.
You should order the side blinds at 42.5cm.

Type B Square bay windows – side blinds full depth

Type B Square bay windows – side blinds full depth

Use this style to cover the side windows more effectively. This is the best style if you want to stop direct light from the sides or to stop people looking in from the sides. There may be a small gap where the front blinds meet the side blinds but this is usually obscured by the window frame at the corners.

Guide for Front Venetian Blind

Measure the width of the recess where the front blind will go. Make sure you take the smallest measurement if the recess or frame varies from top to bottom. Deduct two times the depth according to the slat size of the side blinds (see depth chart). Then deduct 1.5 cm for clearance.

Front bay window recess width 100cm.

Deduct two times the depth for 35mm slats (12cm, to account for the two side blinds) 100cm - 12cm = 92cm.
Then deduct 1.5cm for clearance 92cm - 1.5cm = 90.5cm.
You should order the front blind at 90.5cm.

Guide for Side Venetian Blinds

Measure the width of the recess where the first side blind will go. Make sure you take the smallest measurement of the recess or frame varies from top to bottom. Then deduct 1.5 cm for clearance. Repeat this for the other side bay window blind.

Side bay window recess width 50cm.

Deduct 1.5cm for clearance 50cm - 1.5cm = 48.5cm. You should order the side blind at 48.5cm.

Type C Square bay windows – both recessed for each other – ‘butt up symmetrically’

Type C Square bay windows – both recessed for each other – ‘butt up symmetrically’

Use this method if you do not want the wooden blinds to overlap at the corners or if you require a more symmetrical look. There may be a small gap where the front and side blinds meet but this is usually obscured by the window frame at the corners.

Guide for Front Venetian Blind

Measure the width of the recess where the front blind will go. Make sure you take the smallest measurement if the recess or frame varies from top to bottom. Deduct two times the depth according to the slat size of the side blinds (see depth chart). Then deduct 1.5 cm for clearance

Front bay window recess width 100cm.

Deduct two times the depth for 35mm slats (12cm, to account for the two side blinds) 100cm - 12cm = 92cm.
Then deduct 1.5cm for clearance 92cm - 1.5cm = 90.5cm.
You should order the front blind at 90.5cm.

Guide for Side Venetian Blinds

Measure the width of the recess where the side blind will go. Make sure you take the smallest measurement if the recess or frame varies from top to bottom. Deduct the depth in cm according to the slat size of the front blind (see depth chart). This is to account for the front venetian blind. Then deduct 1.5 cm for clearance. Repeat this for the other side bay window blind.]

Side bay window recess width 50cm.

Deduct depth for 35mm slats (60mm, to account for the front blind) 50cm – 60mm = 54cm.
Then deduct another 1.5cm for clearance 54cm – 1.5cm = 52.5cm.
You should order the side blinds at 52.5cm.

The below is a guide for angled bay windows

This is the trickiest one to measure for, and requires a couple of tools. Nothing huge, all you need is:

  • A tape measure
  • A pencil
  • Some cardboard
  • Some scisrros

Cut 2 pieces of cardboard 30 cm long and as wide as the depth chart dictates. I.e. if you would like 35mm slats then your card board will be 30cm by 6cm. Remember to account for anything protruding from the window, such as a handle. Add the depth of the handle to the overall depth according to the chart. Again, assuming 35mm slats and a 30mm handle your cardboard would be 30cm by 9cm.

35mm slats = 6cm depth.
6cm depth + 30mm handle = 9cm.
30cm by 9cm.

Now that we have our card board guides we can find out our measurements. See the diagram for guidance.

  • Place the strips in the left angle first, and bring them together until the front corners of the cardboard meet. Mark points "A" and "B".
  • Repeat this step for the right side angle, marking points "C" and "D".
  • Lengths 1,2, 3 and 4 should all be the same measurement from the corner.
  • Measure between points "B" and "C" to obtain the width measurement of the centre window treatment.
  • Measure from point "A" outward to the desired width to obtain the width measurement of the left window treatment.
  • Measure from point "D" outward to the desired width to obtain the width measurement of the right window treatment.
  • Deduct about 7.5mm from each of your measurements to allow for clearance.
Measuring Recess Width

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