How to measure for blinds
- Lynne Whitteker
- Consultant
In short
Before you measure, decide on an inside mount, where the blind sits inside the window frame for a clean, minimalist look, or an outside mount, fitted above or around the frame to make the window look larger. Then measure the width and the drop in three places each and, for an inside mount, use the narrowest width and the longest drop. Even a small error can spoil the fit, so the safest option is to have a Russells consultant measure for you.
If you have decided on blinds and want to investigate ready-made or online options, you will need to take your own measurements. Here is a clear guide to getting it right.
Table of contents
Should you choose an inside or outside mount?
This is the first decision to make before any measuring begins, because it changes how you measure. An inside mount sits inside the window frame; an outside mount fits above or around it.
An inside mount offers a streamlined, more minimalist look. The headrail sits back in the frame, accentuating the window and showing off decorative surrounds. The recess needs to be deep enough for the headrail, generally 2.5 to 10cm, and more for vertical blinds so the slats can open.
With an outside mount, the blind is fitted at the top of the frame or on the wall above it. You can hide the fittings behind a decorative pelmet. It is simple to operate, offers more flexibility, and gives the illusion of a larger window.
Still weighing up the two? Our guide on fitting your blinds inside versus outside the frame covers the look and the trade-offs in more detail.
How to measure for Venetian blinds
Once you have chosen your Venetian blinds, measure the width and drop in three places and choose the figures that ensure a clean fit. The method differs slightly for inside and outside mounts.
Inside mount
Measure the depth of the window casing to make sure it is big enough.
Measure the width in three places (top, middle and bottom) from frame to frame, and use the narrowest width.
Measure the height in three places (left, middle and right) from the top of the frame to the sill, and use the longest height.
Outside mount
Measure the exact width where the headrail will sit.
Add at least 10cm for overlap (about 5cm per side) for good light control and privacy.
Measure the height from the top of the headrail location to the sill or where you want the blind to reach, and add about 3cm.
How to measure for vertical blinds
Vertical blinds need a little more depth and an extra diagonal check to confirm the window is square. For an inside mount the recess should be at least 7cm deep for a flush track mount, or 9.5cm for a flush slat mount.
Inside mount
Measure the depth of the casing to confirm it is deep enough.
Measure the width in three places and use the narrowest, and the height in three places and use the longest.
Measure diagonally corner to corner in both directions. If the two measurements differ, choose an outside mount instead.
Outside mount
Measure the width of the window including the frame and add about 7.5cm to each side.
Measure the height from the top edge of the frame to the bottom, or to the top of the sill, and add about 7 to 8cm above for the mounting area.
For floor-length vertical blinds, deduct a centimetre or two so the slats do not touch the floor.
Vertical blinds stack options
Vertical blinds can stack in different ways when open, and this affects your width measurement. For a one-way draw, where all the slats pull to one side, measure the width of the window including the frame and add 7 to 8cm.
How to measure for roller blinds
Roller blinds follow the same approach as Venetians, with the diagonal check used for inside mounts to confirm the window is square.
Inside mount
Measure the depth of the casing, then the width in three places (use the narrowest) and the height in three places (use the longest).
Measure diagonally in both directions. If the measurements are not equal, go for an outside mount.
Outside mount
Measure the width including the frame and add about 7.5cm to each side for light control and privacy.
Measure the height from the top of the frame to the bottom or sill, and add about 7 to 8cm above for the mounting area.
Why precise measurements matter
We cannot stress enough how important it is to be precise. Even a small miscalculation can have a noticeable effect on how the blind looks and works. If you are still choosing between styles, our guide on choosing between curtains and blinds can help you decide. To take the risk out of measuring, request a free in-home consultation and we will measure up and talk you through the options.
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Guides
Choosing the right blinds for your home
Not sure which blinds will suit your home? From blind types and key features to room-by-room advice, this guide covers everything you need to know.
Frequently asked questions
Should blinds be mounted inside or outside the window frame?
Either works. An inside mount sits within the frame for a clean, minimalist look and shows off the window surround, but the recess needs enough depth (around 2.5 to 10cm depending on the blind). An outside mount fits above or around the frame, hides the fittings behind an optional pelmet, and makes the window look larger.
How do you measure a window for blinds?
Measure the width in three places (top, middle and bottom) and the drop in three places (left, middle and right). For an inside mount use the narrowest width and longest drop; for an outside mount add overlap to each side and above for light control and privacy.
How much overlap do outside-mount blinds need?
Add at least 10cm to the width (about 5cm per side) and around 3cm to the drop for good light control and privacy. For vertical blinds, allow about 7.5cm on each side and 7 to 8cm above the window for the mounting area.
Should I measure for blinds myself or get a professional?
You can measure yourself for ready-made or online blinds, but even a small error can spoil the fit and function. A Russells consultant measures your windows precisely during a free in-home consultation, so the blinds fit and operate exactly as they should.
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