DIY Window Measuring: A Straight Answer on the Risk

McCordsville Window Treatments · 2026-09-29

Measuring a window sounds like it should take thirty seconds: width, height, done. It doesn't work that way for custom product, and the gap between a rough number and an order-ready number is exactly where most DIY mistakes happen.

Deciding Inside or Outside Mount Before You Measure

The single biggest decision before you pick up a tape measure is whether the shade or blind is going inside the window frame, or mounting to the wall around it. That decision changes which numbers actually matter, so it has to happen before the tape comes out, not after.

Inside mount means you're measuring the actual opening, the clear space inside the frame where the headrail will sit. Outside mount means you're measuring how far past the frame the finished product needs to extend to cover it properly, which usually means adding several inches to the width and height rather than measuring the opening at all.

If you haven't decided yet, decide before you touch the tape. A window in McCordsville with less than about 2 inches of clear depth inside the frame, or one with a crank handle or lock sticking into that space, generally can't take inside mount at all regardless of what you'd prefer, so check for obstructions first and let that decide the method.

Recording the Numbers Without Wrecking the Order

With a full house of windows to get through, the recording system matters as much as the measuring itself. Round to the nearest eighth of an inch. Write width first, then height. Label every single entry by room and window position, such as kitchen over sink rather than just kitchen, if there's more than one window in that room.

Take a photo of each window with its numbers visible on a sticky note or written on painter's tape stuck to the frame. It takes ten extra seconds per window and it's the easiest way to catch a transcription error before you're filling out an order form for the whole house at once, days later, from memory and a notepad.

Double check the total count at the end. It sounds obvious, but it's an easy step to skip, and a missed window is a common way a full-house order comes up one item short.

What Happens When the Measurement Is Wrong

This part deserves a straight answer instead of a soft one. Custom window coverings are built exactly to the number given, and once they're cut, they generally aren't returnable the way a shelf product is. Get the number wrong and the usual outcome is paying again for a remake, not a refund, because nothing about the product itself was defective.

That's not a reason to avoid measuring your own McCordsville windows. It's a reason to take the process seriously if you do. Straightforward rectangular windows with good access and no obstructions are genuinely low risk. Anything with a visible slope, an uncertain depth, or a long list of windows to get through in one session carries more room for a mistake to slip through unnoticed.

Be honest with yourself at the end of the process. If every number came out clean and consistent across all three measuring points, that's a good sign. If one window left you second-guessing, don't talk yourself out of that feeling. A second check before ordering costs nothing. A remake after a bad order costs real money.

Whatever you decide, get the number right before you order, because a custom shade or shutter doesn't come back once it's cut to a size. A free in-home measure is the simplest way to remove that risk, and it doesn't cost anything to book one.

The Tools That Actually Matter

The baseline tool kit is short: a steel tape measure, a pencil and paper, a stepladder if needed, and ideally a second person. If you've got all four and you're willing to be patient rather than rushing through it, you have what's needed to measure accurately.

What tips the scale toward getting help instead is missing more than one of those things, especially the second person on a wide window, or feeling unsure about reading a tape to the nearest eighth of an inch rather than rounding. Those aren't skills everyone has practiced, and there's no shame in knowing that about yourself before an order that can't be undone goes in.

• Steel tape, not cloth
• Pencil and paper for each number, recorded immediately
• A stepladder for anything above easy reach
• A second person, especially on wide or tall windows

A laser measure only belongs on this list if it reads out in exact fractions. Otherwise it's introducing rounding error into a process where rounding error is the whole problem.

The Three-Point Measure, and Why One Number Isn't Enough

This is the step that separates a careful DIY measurement from a rushed one. Measure width at the top, the middle, and the bottom of the opening. Measure height at the left, the middle, and the right. Write down all six numbers, not an average and not just the middle reading.

The reason is simple: very few window frames are perfectly square, even in newer McCordsville construction. A frame can look dead straight and still be a quarter inch narrower at the top than the bottom. The order gets built to the smallest width of the three and the smallest height of the three, because a shade sized to the largest measurement won't fit into the tightest point of the actual opening.

Skipping this step is the single most common shortcut in a DIY measure, and it's understandable, since measuring once in the middle feels thorough enough. On plenty of windows it is. On enough of them it isn't, and there's no way to know which category a given window falls into without actually checking all three points.

Frequently Asked Questions

Is it obvious if my window frame is out of square?

Not always from looking at it. A frame can look perfectly square and still be off by a half inch between the top and bottom width. That's exactly why the three-point measure matters more than a visual check.

What happens if I write down width and height backwards?

The order gets built to the wrong dimensions entirely, and depending on the product, it may not be a mistake anyone catches until installation. Always write width first, then height, and label both clearly rather than trusting memory.

Is there a benefit to having a second person help measure?

Yes, mostly for accuracy. Holding a tape steady at a top corner while reading a number at the bottom is hard to do alone without the tape sagging or slipping, and a second set of hands solves that.