How to Measure Window Blinds: A Step-by-Step Guide for Renovations, Remodels & Custom Home Builds

Measuring window blinds may seem simple, but getting it right is crucial if you want blinds that fit properly, hang straight, and function smoothly. Whether you’re installing blinds in a new home, replacing outdated ones, or ordering custom window treatments online, accurate measurements are the foundation of a clean, professional look.

This guide walks you through the exact steps you need to take—covering inside and outside mounts, common mistakes, depth requirements, and when to bring in professionals for complex projects.

What You Need Before Measuring Window Blinds

Tools Required

To ensure precise measurements, gather the following:
• A steel tape measure that reads down to 1/8 inch
• A pencil for marking
• A notepad or phone for recording measurements
• A step stool, if measuring tall or hard-to-reach windows

Never use cloth tape measures—they stretch and distort.

Identify Your Mount Style (Inside vs Outside)

Before you measure anything, decide whether your blinds will be mounted:
• Inside the window frame (clean, modern look), or
• Outside the frame (better for privacy, blackout coverage, or uneven windows)

This choice changes your measuring method, so confirm it first.

How to Measure Window Blinds for an Inside Mount

Inside mounts require accurate, tight measurements so the blinds fit neatly inside the opening.

Step 1 – Measure the Window Width

Take three width measurements:
• Top
• Middle
• Bottom

Window frames are rarely perfectly square, so always record all three. Use the smallest measurement—this ensures the blinds fit inside the narrowest point.

Step 2 – Measure the Window Height

Take height measurements in three places:
• Left
• Center
• Right

This time, use the largest measurement so the blinds extend fully to the bottom of the frame.

Step 3 – Measure Window Depth

Depth determines whether your blinds will fit inside the frame without sticking out.
Measure the flat surface inside the window frame from front to back. Make sure obstructions like locks, cranks, or handles don’t interfere with depth clearance.

Step 4 – Document Measurements Correctly

Label each window individually—never assume two windows in the same room are identical. Be consistent with inches and fractions throughout your notes.

How to Measure Window Blinds for an Outside Mount

Outside mounts attach to the wall or window trim, covering more area and giving better light control.

Step 1 – Measure the Width Beyond the Frame

Measure the exact width of the window, then add: 2–3 inches on each side

This ensures better privacy, light blocking, and visual balance.

Step 2 – Measure the Height Beyond the Frame

Add extra height above the window for the blind’s headrail, brackets, or valance. A common rule of thumb: add 2–4 inches above the top of the window.

Step 3 – Consider Trim, Crown Molding & Obstacles

Outside mounts require more surrounding space.
Check for:
• Window trim
• Crown molding
• Light switches
• Curtain rods
• Furniture placement

These factors determine where the blinds can mount safely.

Inside Mount vs Outside Mount: Which Should You Choose?

When Inside Mount Is Best

Choose inside mount if you want:
• A sleek, built-in look
• Minimal visual bulk
• Modern or minimalist aesthetics

Inside mounts are ideal when your window frame is deep and square.

When Outside Mount Is Best

Choose outside mount if you want:
• Maximum light blockage
• More privacy
• The appearance of taller or wider windows
• To cover uneven or shallow frames

Measuring Differences That Affect Your Decision

Inside mounts demand strict, exact measurements.
Outside mounts allow more flexibility but require extra clearance around the frame.

Common Measurement Mistakes to Avoid

Rounding Measurements Up or Down

Never round.
Even a 1/8-inch variation can cause blinds not to fit—or to rub against the frame.

Forgetting to Check Depth Requirements

A blind might technically “fit” width-wise, but stick out awkwardly if the depth is too shallow.

Assuming All Windows Are the Same Size

In reality, almost every window has slight differences—even when they look identical.

Ignoring Surrounding Space for Hardware

Outside mounts often fail because homeowners forget to check for trim, molding, or nearby fixtures.

How Home Renovation Professionals Improve Measurement Accuracy

When to Call a Pro

Consider professional help if you have:
• Bay or bow windows
• Large picture windows
• Arched or specialty windows
• An entire home that needs blind installation

Renovation Expertise Example

Homeowners undergoing a remodel often work with experienced contractors like Elevate Construction Group, who ensure windows are properly framed, leveled, and prepped—making blind measurement and installation more accurate and seamless during renovation.

Custom Home Builds & Window Planning

For custom homes or design-build projects, firms such as Origami Design Build help integrate window sizing, interior layout, and finishing details early in the planning process. This eliminates measurement errors and ensures blinds fit perfectly once construction is complete.

Pro Tips for Getting Perfect Measurements

Measure Twice, Order Once

Always double-check your numbers. A second pass prevents costly mistakes.

Keep Measurements Organized

Label each window by room and location (“living room – left window”). This makes ordering blinds easier and reduces mix-ups.

Consider Future Window Treatments

If you may someday add curtains or layered treatments, plan enough space for additional hardware.

Conclusion

Measuring window blinds the right way ensures a perfect fit, better light control, and a more polished look in your home. With accurate measurements—and a clear understanding of inside vs outside mount—you can confidently order blinds that enhance the style and function of your space.

And if you’re renovating, upgrading, or building a new home, working with qualified professionals can make the entire process smoother. Whether it’s contractors ensuring windows are framed correctly or design-build teams integrating sizing early, proper planning always leads to better results.