How to Measure for Blinds and Shades

New blinds or shades can add to any room in your home. Not only do they provide privacy, but they protect your furniture, floor, and walls from the sun’s UV rays. They also add an element of décor to the room.

Changing window treatments can make your room look entirely new, but before you purchase new ones, you must know how to measure for blinds and shades to ensure a proper fit.

Types of Window Blinds and Shades

When choosing window blinds or shades, you have many options. The type of window and the look you want to achieve will determine the best choice for your windows.

Here are the top options:

  • Horizontal blinds – This is the best option if your room gets a lot of sunlight and you sometimes want to block it out. The blinds’ slats are tilted so you can control how much sunlight enters the room, letting in some, a lot, or no sunlight.
  • Energy efficient blinds – Keeping warm air inside the home in the winter and cool air in the summer keeps everyone more comfortable and saves you money on utility bills. These blinds are attractive yet functional.
  • Blackout shades – If you’re sensitive to sunlight or need shades in a bedroom, blackout shades provide the ultimate protection while giving the room aesthetic appeal.
  • Vertical blinds – Large windows or sliding glass doors need vertical blinds to cover the entire window and make opening and closing the window or door simple.

Options to Install Window Blinds

Depending on the type of windows, you may have options for mounting window blinds and shades, including inside and outside mount.

Inside Mount

If your window allows enough room to install the blinds or shades inside the opening, you can choose an inside mount. When blinds or shades have an inside mount, they cleanly cover the window but don’t go beyond it. You can choose how deep or shallow to install the blinds.

Outside Mount

Outside mount blinds or shades are larger than the window and cover more than the window and trim. These blinds or shades are installed outside the window box and sometimes directly on the window frame.

Is Inside or Outside Mount Blinds Better?

In most cases, it’s a matter of personal preference, but the inside mount is best if the window has decorative trim. However, if the window has a shallow box or you want to hide the trim, you may prefer an outside mount.

Benefits of Inside Mount

  • Inside, mount blinds and shades take up less wall space. If you have minimal wall space in your room, you may prefer that the blinds or shades are inside mounted, leaving room for other wall décor.
  • If you have fancy window frames, you don’t want to cover them with window treatments. Inside, mount blinds or shades ensure you can see the frames and properly cover your window.
  • Inside mount window treatments provide clean lines and a less ‘cluttered look,’ which some people prefer.

Benefits of Outside Mount

  • Mounting blinds or shades outside the window box can give the illusion of a larger or taller window, which may make the room seem larger. Outside mount on large windows also allows you full access to the window if you roll the blinds or shades up.
  • It may be easier to reach the window handles. If your windows have large handles or cranks, you can easily access them with outside mount shades or blinds without moving them up.
  • You’ll let less light in since the blinds or shades cover more than the window. You don’t have to worry about light seeping in through the sides.

How to determine which option is best for your windows

Choosing between inside mount and outside mount largely depends on your specific needs and preferences:

  1. Measure Your Window Depth: Start by measuring how deep your windows are from front to back. If there is sufficient depth, an inside mount can be a great choice.
  2. Assess the Window Frame: Examine the condition and size of your window frame. If it is in good condition and provides enough space for mounting brackets, an inside mount can be an excellent option.
  3. Consider Aesthetic Preferences: Think about the overall look you want to achieve. Inside mounts provide a sleek appearance, while outside mounts offer more coverage and can hide unappealing windows.
  4. Evaluate Light Control Needs: Determine how much light control you require. Inside mounts are better at reducing light gaps, while outside mounts provide enhanced light blockage.

Remember to take accurate measurements before making any decisions. Measure both the width and height of your windows to ensure a proper fit for your blinds or shades.

Step-by-step Guide:

Measuring Window Width and Height

Accurate measurements are crucial. To ensure a perfect fit, you need to measure the window width and height correctly. In this step-by-step guide, we will walk you through the process of measuring your windows like a pro.

Tools needed for accurate measurements

Before you start measuring, gather the following tools:

  1. Measuring tape: A retractable measuring tape is essential for precise measurements.
  2. Pencil and paper: These will come in handy for jotting down your measurements and any additional notes.
  3. Ladder or step stool: Depending on the height of your windows, you may need a stable platform to reach them comfortably.

Measuring for Inside Mount Blinds and Shades

If you’ve decided on inside mount blinds or shades, it’s important to know how to measure the window so you order the proper size.

  1. Take measurements of the window’s width inside the frame at the top, middle, and bottom of the window. Since no construction is perfect, you might get slightly different measurements in each spot. Use the smallest number as your width.
  2. Take measurements of the window’s height inside the frame, on the left, right, and middle of the window, vertically. This time, you’ll use the largest measurement of the three to ensure the blinds or shades are long enough.
  3. Measure the window from the top right corner to the bottom left and again from the top left to the bottom right. These measurements should be similar, if not exact. If they aren’t, you should consider outside mount blinds.

Measuring for Outside Mount Blinds and Shades

Measuring for outside mount blinds requires you to first decide how far out you want the blinds or shades to go. Remember, they will extend past the window trim and frame.

  1. To measure the width, start at the point you want the blinds to go to on the left side and measure to the spot you want them on the right side. Round your measurement to the nearest 1/8th of an inch.
  2. To measure the height, start at the highest point you want the blinds to go at the top of the window and down to the lowest point you want them at the bottom. To control the most light, be sure the blinds or shades go at least 1 or 2 inches above the window.

Measuring for Inside Mount Vertical Blinds

If you have a large window that is wider than tall, vertical blinds may work best. You can choose an inside mount for vertical blinds on windows but not on sliding glass doors.

Here’s how to measure for inside mount vertical blinds.

  1. Measure the widow’s width at the top, middle, and bottom, using the smallest measurement when ordering your vertical blinds.
  2. Measure the window’s height on the left, middle, and right, choosing the largest measurement when ordering your vertical blinds.

Measuring for Outside Mount Vertical Blinds

If you have a sliding glass door or large window, you should consider outside mount vertical blinds with these steps.

  1. Measure the window’s width, adding four inches on each side to limit the sunlight entering the home when you want it dark.
  2. Determine where you’ll install the vertical blinds’ headrail and measure from there to the sill on the window’s left, right, and middle. The headrail should be at least 3 inches above the window.
  3. If you measured to the floor, take ½ inch off the measurements to allow for floor clearance.

Tips for Measuring Blinds and Shades Correctly

  • If your measurements are in between, always measure to the closest 1/8”.
  • Take inside and outside mount measurements if you aren’t sure what you want; this way, when you look at samples, you can choose between both.
  • Don’t use a cloth measuring tape; a steel tape provides more accuracy.
  • When writing your measurements, put the width first, then the height.
  • If you aren’t sure if you are measuring right, leave it to the professionals, as custom blinds cannot be returned.

Common mistakes often made when measuring for blinds or shades include:

  1. Using Inappropriate Measuring Tools: Inaccurate measurements often occur when a tape measure that is not long enough or a ruler is used instead of a steel tape measure.
  2.  Failure to Measure in Three Places: Windows aren’t always perfectly square. Measuring only one spot might result in a blind or shade that doesn’t fit properly.
  3.  Ignoring the Mounting Style: Inside and outside mount blinds and shades have different measurement requirements. Mixing them up can lead to blinds or shades that are too large or too small.
  4. Overlooking the Window Depth: Certain types of blinds and shades need a specific window depth for an inside mount installation. Ignoring this can lead to improper fitting.
  5. Failing to Allow for Overlap on an Outside Mount: If installing outside mount blinds or shades, failure to account for an overlap can result in light leaks around the edges and a compromise in privacy.
  6. Not Double Checking Measurements: A simple measuring mistake can be costly since blinds or shades that have been cut usually can’t be returned.
  7. Neglecting Manufacturer’s Instructions: Each manufacturer might have specific requirements for their products. Overlooking these instructions can result in ill-fitting blinds or shades.

How to Measure Different Types of Windows

Different types of windows require specific measuring techniques to achieve optimal results:

  • Double-hung windows: For these traditional windows with two vertically sliding sashes, follow the same steps mentioned earlier for measuring width and height.
  • Casement windows: These windows open outward on hinges like doors. When measuring casement windows for inside-mount blinds, take care not to obstruct their movement when installing blinds within the frame.
  • Bay or bow windows: These curved or angled windows add architectural interest but can be challenging to measure accurately due to their unique shape. To measure bay or bow windows correctly:
    1. Measure each individual section of the bay or bow window, including the width and height.
    2. Note down any angles or curves within the window frame.
    3. Consider whether you want a single blind to cover the entire bay/bow or individual blinds for each section.


How can I tell what size blinds I need?

The best way to tell what size blinds you need is to have a professional measure your window. This is the best way to avoid mistakes and to ensure a proper fit. Before ordering blinds or shades, you must determine if you want an inside or outside mount. Look at your different options and ask for samples when available.

How much smaller should the inside mount blinds be than the window?

It’s important to always use the narrowest measurement when choosing inside-mount blinds. To err on the side of caution, cut your blinds ¼” smaller than your smallest measurement.

How do you measure for blinds inside a frame?

Always measure the window’s width first and then the height. Measure in three spots to account for any variations in construction to ensure the blinds fit.

Will my blinds or shades provide enough privacy?

Privacy is essential in any home. When measuring for blinds or shades that offer optimal privacy levels, consider the following:

  • Inside Mount: This installation method provides a snug fit within the window frame, minimizing light gaps and maximizing privacy.
  • Outside Mount: Opting for blinds or shades that extend beyond the window frame ensures better coverage and enhanced privacy.

By selecting the right style and installation method, you can achieve both privacy and an aesthetically pleasing look in your room.

What if my windows have limited depth?

If your windows have limited depth, it’s important to choose blinds or shades that can accommodate this constraint. Look for options specifically designed for shallow windows or consider alternative solutions such as:

  • Roller Shades: These are an excellent choice for windows with limited depth as they roll up neatly at the top.
  • Cellular Shades: Their compact design allows them to fit snugly within shallow window frames while still providing insulation benefits.

Final Thoughts

Knowing how to measure for blinds and shades is important. If you measure incorrectly, you could end up with blinds or shades that don’t fit. Since window treatments protect the home from the sunlight and provide privacy, you want an accurate fit to ensure the utmost energy efficiency.

Now that you have learned how to measure for blinds and shades effectively, it’s time to put your newfound knowledge into action. Measure your windows confidently knowing that you have the tools to achieve an impeccable fit.