The short answer: grab a metal tape measure (not fabric, it stretches), measure the width in three spots and the height in three spots, and always go with the smallest width and the longest height. That’s the golden rule that saves 90% of people from ordering blinds that don’t fit. Now let’s get into the details so you get it right the first time.
Measuring for blinds sounds simple until you’re standing there with a tape measure wondering if you’re supposed to measure inside the frame or the whole window. We’ve walked hundreds of customers through this exact process, and honestly, most mistakes come down to skipping one small step. Here’s how to avoid that.
What You’ll Need
- A steel tape measure (fabric tapes bend and give inaccurate readings)
- A pencil and paper, or your phone’s notes app
- A step stool if your windows are tall
- Someone to help hold the tape steady (optional but makes life easier)
Step 1: Decide Inside Mount or Outside Mount
Before you measure anything, figure out which way you’re mounting the blinds.
Inside mount sits within the window frame, giving you a clean, built-in look. You need at least 2 to 2.5 inches of depth in the frame for this to work.
Outside mount sits on the wall or trim above the window, covering the whole frame. This is the better choice if your frame is too shallow, uneven, or you simply want more light blocked.
If you’re not sure which one suits your window, that’s completely normal, most people aren’t. It’s worth checking your frame depth before you commit either way.
Step 2: Measure the Width
For an inside mount, measure the width at the top, middle, and bottom of the window opening. Window frames are rarely perfectly square (even in newer homes), so these three numbers are often slightly different.
Use the smallest of the three measurements when you place your order. Blinds are made to fit inside the frame, so if you go with the widest number, they might not fit at all.
For an outside mount, measure the width of the area you want the blind to cover, and add at least 3 to 4 inches on each side for better light coverage and privacy.
Step 3: Measure the Height
Same idea here. Measure the height on the left side, center, and right side of the window.
This time, use the longest measurement. It’s fine if the blind sits slightly lower on one side since it’s barely noticeable, but a blind that’s too short will leave a gap you’ll see every single day.
For outside mount, measure from where you want the top of the blind to sit down to where you want it to end, and add a few extra inches at the top for proper coverage.
Step 4: Check Your Depth (For Inside Mount)
Measure how deep your window frame is at a few points. If your frame is shallower than 2 inches, an inside mount might not sit properly, and an outside mount will look better and function better anyway.
Step 5: Note Any Obstructions
Look for handles, cranks, locks, or uneven trim that might get in the way of the blind opening and closing smoothly. This is the step people forget most often, and it’s the one that causes headaches after installation.
Step 6: Write Everything Down Clearly
Label each measurement with the room and window (like “Kitchen, window facing backyard”) so nothing gets mixed up when you’re ordering multiple blinds for multiple rooms. Trust us, it’s easy to forget which number belonged to which window once you’ve measured your whole house.
A Few Things We Always Tell Our Customers
Measure twice. It sounds like a cliche, but it genuinely prevents most fitting issues. Also, measure in inches to the nearest eighth if you can, since small fractions matter more than people expect. And if a window looks even slightly off square, it probably is, so don’t skip the three-point measurement out of confidence that your walls are perfectly straight.
Not every window is a standard shape either. Bay windows, arched windows, and French doors all need a slightly different approach, and that’s genuinely where getting a professional opinion helps more than guessing.
Quick Recap
- Always measure width and height in three spots each, using the smallest width and the longest height
- Decide between inside mount and outside mount before you measure, since it changes your approach
- Check your frame depth if you’re going with an inside mount
- Watch out for handles, locks, and trim that could get in the way
- Label your measurements clearly if you’re doing more than one window
Measuring can feel like the trickiest part of getting new blinds, but once you’ve done it once, it clicks. And if you’d rather skip the guesswork altogether, our team at Ace Blinds is happy to help you get it right, from measuring to installation. Reach out to us today and we’ll take the stress out of it for you.