Accurate Measurements: A Step-by-Step Guide on How to Measure for Blinds

Accurate Measurements: A Step-by-Step Guide on How to Measure for Blinds

If you have ever needed to measure your windows for blinds, you'll know it's not as simple as measuring from A to B. What if your window is shaped oddly, in an arched or circular form? And even if your window is a regular rectangle – how should you measure for inside-mount vs outside-mount blinds?

Here, we'll unpack the ins and outs of how to measure for blinds accurately for optimal light control. Let's walk through some simple instructions step-by-step.

Tools and Materials Needed

There are a couple of items you'll need to have on hand before beginning your measurements:

  • A steel tape measure. It's best to use a steel measuring tape specifically, since fabric tapes stretch and aren't always accurate.
  • A pencil and paper. You'll need to make a note of your measurements as you go along.
  • A leveler or spirit level (if measuring for outside mount blinds). This will help ensure that the blind is installed perfectly vertical if mounted on an exterior wall.
  • A ladder. You'll need to be able to reach the top of the window in order to measure it properly.

Collect these items before you begin so that you don't have to pause your measurements.

How to Measure for Inside-Mount Blinds

Inside mount blinds are so-called because they sit within the window frame as opposed to outside of it. Here's how to measure for them:

  1. Use the metal tape measure to find the width of the inside of your window frame at its top, middle and bottom. Make sure that you are measuring from one inside edge to another – not from the outer edges of the window trim frame.
  2. Measure the height (also known as the drop) of the window frame at its left, middle and right side. This means from the bottom-most part of the frame on the top of the window to the top-most part of the frame on the bottom of the window.
  3. Note down your measurements for each side and use the smallest measurement you have taken; this will be the size of blind that will fit within your window frame.
  4. Make sure you also measure the depth of your window frame, too, just in case the headrail is too thick for the minimum depth requirement.

To get the most accurate measurements possible, make sure that you measure at three different points for both the width and the height spaced out across the entire window. You can't always rely on the window frame being perfectly even all the way around, so it's best to err on the side of caution.

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How to Measure for Outside-Mount Blinds

Outside mount window blinds are mounted onto the wall above and/or beside your window as opposed to within it. Here's how you measure for them:

  1. Measure the width of your window from one outside edge of the window casing to another. If your window has architraves, measure from the outermost edges of these in order to get the most accurate measurement. Take this measurement across the top, middle, and bottom of the window.
  2. Measure the height of your window from top to bottom window sill, again making sure you measure from one outside edge to another. Take this measurement from the left side, the right side, and the middle of the window.
  3. Note down your measurements for each side and use the largest measurement you have taken; this will be the size of blind that is necessary to cover your window plus some extra space around it.
  4. Make sure you also measure the window depth of the window recess and any protrusions around your windows, such as architraves, just in case!

It's best to use a leveler or spirit level when measuring for outside mount blinds, as it will help you to make sure that the blind is installed perfectly straight. Remember that outside-mount blinds should overlap your window in order to block out light properly – so if you are measuring for blackout, plan accordingly!

Measuring Guides for Specialty Shapes & Types

If you have specialty windows in your home that don't meet standard window sizes or don't have straight-cut edges, such as perfect arches or an eyebrow arch with legs, you can actually get custom window coverings made to fit them perfectly. However, you will need to measure the window accurately in order to do so.

Perfect arches are quite simple; once you measure the width of the arch, the height is simply half of the width. Your blinds manufacturer will be able to craft the curve based on those two measurements.

For eyebrow arches, however – which look like a perfect arch at the top and then have two legs at the bottom – you'll need to measure each part of the arch separately. Measure the width and height of the rectangular part as you would for a regular window, then measure the height and width of the arch.

If your window has a pronounced architrave between the arch and the rectangle, you'll measure the height of the architrave and subtract it from the final total height.

When you're measuring for specialty shapes, remember that professional window fitters and installers may be able to help you with the process.

Double Checking and Recording Measurements

Whenever you choose to measure your windows for blind installation, always make note of the measurements either on your phone or on paper. It's recommended to measure each window twice and compare the measurements before writing them down, as this will help ensure accuracy and save you time in the future.

When measuring for any type of outside-mount window treatments – including specialty shapes – use a level to ensure that the headrail and installation brackets will be mounted parallel to the floor.

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Custom-Made Blinds For Your Home

Measuring your windows with accuracy is one of the most important steps in getting custom-made blinds for your home. Once you have the measurements, you can pick out the right type of blinds and materials to suit your needs and style preferences, as well as find a reliable manufacturer or supplier who will craft them for you.

Once that's done, all there's left to do is install! With accurate measurements, installing new blinds in any shape or size window should be a breeze.

At Factory Direct Blinds, we've got years of experience crafting custom-made blinds for any shape and size windows. Contact us today to get started on your window treatment project!


Do blinds have to be exact size?

Yes; in order to maintain their proper fit and function, blinds must be the exact size you measure for. Outside-mount blinds have a bit more leeway, as they don't need to fit within the window frame, but the measurements should still be as accurate as possible.

Can I measure windows for blinds myself?

Yes; measuring windows for blinds is actually a relatively straightforward process that can be done with minimal tools and some basic instructions.

What size blinds do I need for a 35-inch window?

The size of blinds you need for a 35-inch window depends on whether you are installing inside-mount or outside-mount blinds. Inside-mount blinds should be slightly smaller than the width of the window, while outside-mount blinds can be larger. For exact measurements, follow the guidelines in this article.

How do you measure for blinds inside the recess?

Measuring for blinds inside the recess involves taking precise measurements of each side, from the innermost edge of the window frame to the opposite side.

Should blinds be lighter or darker than walls?

Blinds should be slightly lighter or darker than the walls in order to provide contrast and make them stand out. Choosing a color that is too close to the wall color might cause your blinds to blend in and get lost.

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