How to Measure for Blinds and Shades

*Updated September 17th, 2025

Installing new blinds and shades is an excellent way to refresh any room in your home. Beyond enhancing privacy, they protect your furniture, floors, and walls from harmful UV rays, helping to prevent fading and damage. Plus, the right blind or shade can add a stylish finishing touch to your décor, tying the entire room together.

Whether you’re aiming for a sleek, modern look or a cozy, traditional vibe, properly fitted window treatments are key to achieving your vision. Before you buy, it’s essential to measure your windows accurately. Precise measurement ensures a perfect fit for your window blinds, saving you time, money, and frustration from returns or adjustments.

In this guide, you’ll learn how to measure windows for blinds, including both inside mount and outside mount options. With the right approach, you’ll be ready to choose and install the perfect custom blinds and shades for your space.

Types of Window Blinds and Shades

When choosing blinds for windows, the type of window and the look you want to achieve will determine the best choice.

• Horizontal blinds – Best for controlling sunlight with tilting slats.

• Energy-efficient blinds – Reduce heating/cooling costs while looking stylish.

• Blackout shades – Provide full light blockage for bedrooms or media rooms.

• Vertical blinds – Perfect for sliding doors or large windows for blinds.

Options to Mount Blinds

Inside Mount Blinds

If your window frame has enough depth, you can install blinds inside the window. An inside mount offers a clean, built-in look while preserving decorative window trim.

Outside Mount Blinds

Outside mounts require the blind to be installed outside of the window frame, extending beyond the window casing. This makes the window appear larger and provides better light control and privacy.

Tip: Adding 3 inches above the window or to each side ensures maximum coverage and optimal fit.

Measure Your Windows: Step-by-Step

Accurate measurement is the most important step. Always measure the width and measure the height of your windows at multiple points to avoid surprises.

Tools You’ll Need

• Tape measure (avoid cloth; use steel for accuracy)

• Pencil & paper

• Ladder or step stool

1. Measuring for Inside Mount Blinds

• Measure the width inside the frame at the top of the window, middle and bottom. Use the smallest measurement for accuracy.

• Measure the height on the left, middle and right side, using the largest number.

• Measure the depth of your window frame to ensure the mounting brackets and headrail fit.

If your window isn’t perfectly square, you may need to use an outside mount.

2. Measuring for Outside Mount Blinds

• Measure the window area you want covered—add 1 to 2 inches on each side of the window opening.

• Extend 3 inches above the window to block light effectively.

• Note where the brackets and spacer blocks will attach.

3. Measuring for Vertical Blinds

• For inside mount vertical blinds, measure the width at the top, middle, and bottom, then use the smallest measurement.

• For outside mount vertical blinds, measure the width of the area plus 4 inches on each side for better coverage.

Shades Measuring Tips & Common Mistakes

• Always measure in three places—top, middle, and bottom.

• Round up to the nearest 1/8″.

• Don’t forget the window depth—some custom window treatments require more clearance.

• Double-check all exact measurements before ordering.

Mistakes to avoid:

• Using the wrong tools (cloth tape).

• Forgetting overlap for blinds outside the window.

• Skipping manufacturer instructions on how to measure.

How to Measure Different Windows

• Double-hung windows: Standard measure the inside steps.

• Casement windows: Ensure the blind or shade doesn’t block crank handles.

• Bay or bow windows: Measure windows for blinds individually—sometimes it’s best to install multiple mini blinds for a clean look.

Final Thoughts

Taking the time to measure windows for blinds correctly ensures your blinds and shades fit perfectly, provide optimal light control, and enhance your décor. Whether you choose faux wood blinds, vertical blinds, or custom window treatments, proper measurements will guarantee a polished result.

Now that you know how to measure for blinds, you can order with confidence and enjoy stylish, functional windows for blinds that look and perform beautifully.

FAQ

How can I tell what size blinds I need?
Have a professional take exact measurements, or follow this guide to measure your windows carefully before ordering.

How much smaller should inside mount blinds be than the window?
Cut your window blind about ¼” smaller than the smallest measurement.

What if my window has limited depth?
Choose blinds that fit your window space or use extension brackets. Options like roller shades and cellular shades are great for shallow frames.

Additional Window Resources

• How to Choose the Best Windows for Cold Weather Climates
• Top Signs It’s Time to Replace Your Home Windows
• 12 Questions to Ask a Window Company