How to measure Blinds


GENERAL OVERVIEW: Measure Twice & Order Once

Measuring your windows for Blinds, Shades, or Shutters is simple! Here are some easy tips for any kind of window covering we sell. Just remember, it’s always best to check your measurements two times to make sure they’re right before you buy anything. This way, you only have to order once and get it right the first time.

Learn how easy it is to measure your own windows for blinds

Guide to Measuring for Inside Mount and Outside Mount Blinds

  1. Best tape measure for measuring blinds

    Always use a steel tape measure at minimum width of 1inch. We prefer the Stanley Fat Max or a 25 Foot Klein Tools Tape Measure with Double Hook & Magnet. Never try to measure your windows with a cloth tape, ruler or yardstick or you will get an inaccurate measurement. Understand the fraction lines on your tape measure. Only measure in inches. Please look at video “How to read a tape measure.”

    Using fraction measurements using a tape measure

  2. Measuring Inside Mount Blinds

    Before diving into the specific steps for measuring inside mount blinds, it’s crucial to understand the importance of precision. Inside mount blinds are installed within the window frame, offering a clean, built-in look that complements the room’s aesthetics. This mounting style requires accurate measurements to ensure the blinds fit snugly within the window frame without any obstructions. Ensuring your window frame has enough depth to accommodate the blinds’ mounting hardware is also vital. Check with

  3. Measure the window opening

    Always take measurement width x height. (NOT height by width) This is the number mistake people make when measuring for blinds. Measure exact window opening measurements to the nearest 1/8″.

  4. Measure the Width Inside the Window Frame

    This explanation works well with drywall. Put the plate of the tape measure at the left top edge in the inside of the window opening, right at the corner bead or inner edge of bull nose. Measure the window opening width at the top, middle and bottom. Write down the smallest measurement.
    Measuring a big window width with Klein Tools Tape Measure

  5. Measure the Height inside the Window Frame

    Measure the height from the sill up to the top for the inside of the window frame. Measure in three locations. Left, middle, and right. Write your measurement down.

  6. Enter Size at to get a price & place your order

    Navigate to the Product Page: Go to the website and find the blinds or screens you want to purchase. Click on the product to go to its specific page.
    Enter Dimensions: Look for the ‘Size’ or ‘Measurements’ field on the product page. Enter your width and height measurements as obtained in steps 3 and 4. Ensure you’re entering the dimensions in the specified units (inches only).
    Select Additional Options: Depending on the product, you might need to choose colors, materials, and other preferences at this stage.
    Adding your sizes width by height to get a price and order your blinds

  7. Measuring Outside Mount Blinds

    Measuring for outside mount blinds involves taking accurate measurements of the window to ensure the blinds cover the entire window and provide the desired privacy and light control. The process can vary slightly between measuring for horizontal blinds (like Venetian or roller blinds) and vertical blinds due to their different orientations and mounting requirements. Here are step-by-step instructions for both:

  8. For Horizontal Blinds:

    When it comes to covering your windows with horizontal blinds, starting with precise measurements is essential. Horizontal blinds, including Venetian, mini, wood and faux wood blinds, offers optimal light control. Best privacy and light coverage is to install your blinds outside mount. Another reason to install your blinds outside mount is when the window is out of square more then one inch. Also, you can lift blinds all the way up but it will have a large stack of slats at the top of the blind below the headrail.

  9. Measure Width for Outside Mount Blinds

    Use a steel tape measure for accuracy. Measure the width where you’ll mount the blinds. This could be the outer edges of the window frame or a wider area if you want more window coverage. Consider any obstructions like handles or moldings and ensure the blinds will not interfere with their operation. Add an extra 1.5 to 3 inches on each side of the window frame for better light control and privacy, this will be your final width measurement.

  10. Measure Height for Outside Mount Blinds

    Measure the height from where the top of the blinds will be installed down to where you want the blinds to end. For better coverage, consider extending the blinds 2 to 3 inches above and below the window frame. If the window sill protrudes, measure to the top of the sill; if not, add length for the blinds to hang freely, typically an extra 1.5 to 3 inches below the window.

    For the bottom stack of slats to clear above the window, check the manufacturers specification on slat stack including headrail.

  11. Consider the Mounting Requirements:

    Check the product specifications for the minimum depth required for mounting brackets, headrail and slats. Ensure the space where you plan to mount the blinds has enough depth to accommodate the headrail and mounting hardware. Check with manufacturer on specifications for depth.

  12. Decide on Valance and Overlap:

     If your blinds come with a valance, consider its size when deciding how high above the window to mount the blinds. The side overlaps (extra width on each side) help with light control and privacy.

  13. For Vertical Blinds:

  14. Measure Width for Vertical Blinds

    Determine where the headrail will be installed. This could be on the wall above the window or on the ceiling. Measure the width from where the headrail will be installed. If there’s no frame, decide how much you want the blinds to overlap the window on each side, typically 1.5 to 3 inches. Consider the opening direction of the blinds and any potential obstructions.

  15. Measure Height for Vertical Blinds

    Decide if the blinds will hang to the floor or just below the window sill. Some sill stick out further then window. In this instance your may consider measuring to the sill and having a 1/4 inch space at the bottom. A full outside mount with sill will require extension L brackets. For blinds hanging to the floor, leave about a half-inch gap to prevent dragging. Measure from the top of where the headrail will be installed to your desired length.
    how to measure vertical blinds

  16. Check for Obstructions:

    Ensure there are no obstructions that would interfere with the operation of the vertical blinds, such as handles, ledges, in window air conditioners or radiators.


What’s the best method to accurately measure the dimensions of existing blinds?

To accurately gauge the dimensions of existing blinds, industry experts underscore the importance of precision and the correct tools. A steel tape measure is recommended for its reliability and accuracy. “The key to precise measurements lies not just in the tool but in the method,” explains Alex Johnson, a professional blind installer with over 15 years of experience. He advises, “Always measure the width from end to end at the top of the blinds where it’s most consistent, and for the height, include every component from the top of the headrail to the bottom of the slats or fabric.” Johnson further emphasizes the significance of double-checking measurements to mitigate errors, a practice echoed by numerous installation guides[1][2]. Documenting these measurements clearly, distinguishing between width and height, is essential for ensuring the perfect fit for replacement blinds or adjustments.

[1] “Measuring for Window Blinds,” Home Improvement Central, 2023.
[2] “Blind Installation Guide,” DIY Network, 2023.

Deciding Between Inside and Outside Mount Blinds: Factors to Consider for the Perfect Fit

Choosing between inside and outside mount blinds hinges on several key factors that affect both aesthetics and functionality. Inside mounts are sleek and fit within the window frame, providing a clean, integrated look that complements modern and minimalist interiors. This option is ideal when you aim to showcase attractive window molding or when space around the window is limited. However, it requires a sufficient window depth to accommodate the blinds’ hardware. On the other hand, outside mounts are mounted on the wall or molding above the window, offering greater flexibility in window coverage. This makes them suitable for windows with shallow depths or for covering unattractive window frames. Outside mounts can also make windows appear larger and hide imperfections in the wall. “The choice often comes down to the desired aesthetic and functional needs,” notes Emma Thompson, a seasoned interior designer. “While inside mounts offer a tailored look, outside mounts provide versatility and enhanced light blocking capabilities.” Thus, when deciding, consider the window’s architectural features, the room’s design scheme, and the level of light control and privacy needed.

What is the recommended width difference between inside mount blinds and the window opening?

When it comes to inside mount blinds, achieving the perfect balance between snug fit and operational ease is key. Typically, the recommended width difference between the blinds and the window opening should be minimal to ensure a neat, flush fit within the frame. However, it’s important to account for the manufacturing tolerances specified by the blind manufacturer. Most manufacturers automatically deduct a small fraction of an inch (usually around 1/8″ to 1/4″) from the width of the blinds to prevent them from scraping the sides of the window frame when operated.
For instance, if your window opening measures 35 inches wide, and you order blinds to match this width, the manufacturer will likely make the actual width of the blinds slightly less—34 3/4″ to 34 7/8″, for example—to ensure they can move freely without obstruction. This slight deduction is crucial for the blinds’ functionality but is small enough to maintain privacy and light control. As such, when measuring for inside mount blinds, provide the exact window opening size and let the manufacturer make the necessary adjustments for the best fit. This approach eliminates guesswork and ensures a professional, seamless look once the blinds are installed.

Choose Inside or Outside Mount:

Before taking any measurements, step back from your window and decide if you want to mount the window treatment inside the window recess or outside on the wall or molding. For an inside mount, the window opening must have enough unobstructed depth to allow mounting. Be sure to look for obstructions like window locks, window cranks, etc.

How To Measure Inside Mount Blinds

Measure Window Frame Opening for IB Inside Bracket / Mount

Measure your window horizontally in three places: top, middle, and bottom. Order the smallest size measurement. DO NOT take any deductions, the size you order will come with a 1/2-inch deduction to allow the blind fits in your window frame properly.

The window frame needs to be at least 2 inches deep to install as inside mount

How To Measure Outside Mount Blinds

Measure 2 to 4 inches past the frame for OB Outside Bracket / Mount

Measure width of your window horizontally in three places: top, middle, and bottom. Use the largest measurement and ADD 2 to 4 inches on both sides of your window and to the length, to allow for full coverage. The size you order is the exact size you will receive.

Sometimes mounting on moldings is an option for outside mount. See the how to install a cordless faux wood blind video on how this type of install looks. We then measure the moldings exact measurement width by height.

Tip: For a flush inside mount (the blind completely recessed so that no part of the blind projects out of the opening) check that you have enough depth and make sure that if a valance is included that we make it slightly smaller than the window opening width since they are normally made an inch or two wider.


Tip: We usually recommend an inside mount whenever possible because it provides a cleaner look.

However, an outside mount can make a window appear larger or hide an unattractive window.

When you specify inside mount, we will make a size deduction to allow for operating clearance. With most products we will deduct up to 1/4″ from each side. Roller shades also have a rather large fabric and roller tube deduction (see product specs tab on product pages).

For vertical blinds there is also a height deduction of 1/4″. The deductions are made so that the blind will not rub or scratch your window frame. If you specify an outside mount, we will not take any size deductions.

Your blind will be made at the exact size you specify. So you must ADD to the opening measurement to allow for overlap and mounting brackets. When measuring, don’t be surprised if your windows are not square. It’s not uncommon and probably won’t be noticeable.

Go to Home Page

Leave a Reply

Your email address will not be published. Required fields are marked *

Shopping Cart