How to measure window glass for replacement

The short version

Measure the glass you can see - the clear part inside the frame - width first, then height. That is it. You do not measure the frame, you do not add anything, and you do not need to be precise to the millimeter. The glass we order is about an inch larger in each direction because the edge hides under the frame, and we add that for you. With your two numbers (and ideally a photo), we can give you an exact installed price for our foggy glass replacement - no visit needed to get the number. For a standard double-pane window that runs $365 to $825.

What "the glass you can see" means

When the glass was made, its edge was set into a channel in the frame or sash and sealed in place. So an inch or so of glass around the whole perimeter is hidden from view. The part you can see is called the daylight opening (because it is the part that lets daylight through). The true size of the glass behind the frame is called the order size.

Here is the useful part: for nearly every standard window, the order size is just the daylight opening plus about one inch of width and one inch of height. That relationship is reliable enough that we can quote you a real, firm price from the daylight measurement you take yourself - which is why you never have to do the math or guess at the hidden edge. You measure what you can see; we handle the rest.

How to measure, step by step

1. Measure the width. Hold a tape measure horizontally across the visible glass, from where it disappears under the frame on the left to where it disappears on the right. Read it to the nearest quarter inch and write it down.
2. Measure the height. Now go top to bottom of the visible glass, edge to edge. Write that next to the width. Your note should read something like 28 x 42.
3. Note the glass type (optional). Is it single-pane or double-pane? Are there decorative grids between the panes? Any tint? A brand sticker in the corner of the sash? None of this is required, but it sharpens the quote.
4. Get your price. Put the two numbers into our calculator, or text them with a photo. You get an installed price back - one number, not a vague range.

Single-pane or double-pane?

Most homes built or re-windowed in the last 30 years have double-pane (insulated) glass - two sheets of glass with a sealed air or argon gap between them. That gap is what fogs up when the seal fails. To check: in a dim room, hold a small flame or pen light a few inches from the glass at an angle. Two reflections means single-pane; four reflections means double-pane. You can also look at the edge where the glass meets the frame - a double-pane unit has a visible spacer bar (often metal or black) sandwiched between the two panes. If you can tell us which one it is, great; if not, a photo of the window usually tells us.

When self-measuring is enough - and when we take a look first

For a standard rectangular window - the vast majority of foggy and cracked-glass calls - your two measurements and a photo are all we need to quote you an exact price. A few situations are worth a quick confirmation before we lock a number:

• Tempered (safety) glass - required by code near doors, tubs, showers, and stairs. It costs more and cannot be cut to size on site, so we confirm it is needed. Look for a small etched stamp in a corner of the glass.
• Decorative grids or muntins between the panes - these change the unit and the price.
• Odd shapes - half-rounds, arches, triangles, or anything not a plain rectangle.
• Some Pella and Andersen units - certain series use proprietary sizes and clips, so we match the spec carefully. (See our Pella and Andersen guides.)

Even then, the worst case is a short conversation or a photo - not a wasted afternoon waiting on a measuring appointment. And no matter how we quote, once you approve it we come out and take the final, to-the-eighth-inch measurement ourselves before any glass is ordered.

Common measuring mistakes

• Measuring the frame instead of the glass. Measure the clear glass only - we handle the hidden edge.
• Adding the inch yourself. Do not. Give us the daylight (visible) size and let us convert it, or you will double-count.
• Width and height swapped. Always width first, then height, so the quote matches the window.
• Measuring from the outside. Measure from inside the house where you can see the true edge of the glass.

Next steps

You have your two numbers - now turn them into a price. Drop the width and height into our cost calculator for one exact figure, or text us a photo and the measurements and we will text back your installed price, usually the same day. Not sure what is wrong with the window in the first place? Start with the 30-second Window Health Check.