How to Measure Your Own Windows for Blinds or Shades

Avon Window Treatments · 2026-09-29

Every custom order starts with a number, and that number comes from somewhere. Sometimes it's a professional with a steel tape and a level, and sometimes it's an Avon homeowner standing on a step stool with a cloth tape from a sewing kit. Both can work. Only one of them has much room for error.

Deciding Inside or Outside Mount Before You Measure

If you're measuring a whole house in one sitting, walk every room first and make the mount call before you touch a tape anywhere. It's a lot faster to sort all your windows into inside mount and outside mount piles up front than to bounce back and forth between decisions room by room.

Inside mount needs a clear opening with real depth, usually at least 2 inches, and nothing like a crank or lock intruding into that space. Outside mount works around most of those limitations by mounting to the wall or trim instead of fitting inside the frame. A quick walk-through of an Avon house, checking depth and obstructions on each window, usually sorts most of them in under fifteen minutes.

Write the mount decision down next to each window as you go. You'll need it again in a few minutes once the actual measuring starts, and re-deciding it twice wastes time you don't need to spend.

Recording the Numbers Without Wrecking the Order

Rounding to the nearest inch instead of the nearest eighth is a quiet way to sabotage an otherwise careful measurement. It feels close enough. It isn't, and that gap is enough to leave a visible light gap on one side or keep a shade from clearing the frame on the other.

Writing height where width goes, or the other way around, is the other classic failure, especially late in a long measuring session when fatigue sets in and every window starts to blur together. Always write width first, then height, and label both clearly rather than trusting that you'll remember the order by the time you sit down to fill out the actual form.

If you're doing more than two or three Avon windows in one sitting, build in a system before you start: room name, smallest width, smallest height, mount type, written down together for each window before moving to the next one. Skipping that system is how a homeowner ends up with eight sets of numbers and no idea which belongs to which room.

What Happens When the Measurement Is Wrong

This is the part worth being straight about. Custom window coverings are built to the exact number you provide, and once they're cut and assembled, they generally can't be returned the way a stock item can. If the number's off by enough to matter, you're looking at paying for a remake rather than getting a refund, since the mistake was in the measurement, not the product.

That doesn't mean measuring your own windows is a bad idea. Plenty of Avon homeowners do it successfully every year, especially on straightforward rectangular windows with clear access and no obstructions. Where it gets risky is on anything unusual: a window with visible slope, one where you're not sure if there's clearance for inside mount, or a room with enough windows that one bad measurement is easy to lose track of among the rest.

If you've gone through the process and you're confident in the numbers, that confidence is usually earned and worth trusting. If something about a specific window feels uncertain, that's exactly the situation a second set of eyes is good for, and it costs nothing to have someone check before an order that can't be undone goes in.

Measuring your own windows is a reasonable thing to attempt, as long as you go in knowing a custom order can't be undone if the number's off. If any part of the process feels uncertain, a free in-home measure is there to double check the work before you order.

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 Avon 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

Should I measure to the nearest inch or the nearest fraction?

Nearest eighth of an inch, every time. Rounding to the nearest inch feels close enough but it isn't, since a quarter inch of slop is often the difference between a shade that fits and one that doesn't clear the frame or leaves a visible gap.

What kind of tape measure should I use?

A steel tape, not a cloth one. Cloth tapes stretch slightly with use and age, which throws off a measurement just enough to matter on a custom order. A basic steel tape from any hardware store is accurate and cheap.

Do I measure the glass or the whole frame?

Neither, exactly. For inside mount you measure the inside of the frame opening itself, not the glass and not the outer trim. For outside mount you're measuring how far past the frame you want the covering to extend, which is a different number entirely.