Accurate measurements are the foundation of a window replacement that fits and seals properly. Here’s how measuring replacement windows actually works, and why it’s worth leaving to a professional. Our professional window installation services handle every measurement with precision.
Why Precise Measurements Matter
A window that’s even slightly mismeasured can lead to gaps around the frame, difficulty opening or closing, or a seal that fails well before it should. Getting the measurements right the first time avoids costly delays, since custom-sized windows built to inaccurate dimensions typically can’t be adjusted after the fact.
This matters even more on older homes, where openings can shift slightly out of square over decades of settling, making an accurate, careful measurement more important than simply reading a tape measure once and moving on.
Measuring Width: Brick to Brick
For most exterior window openings, the standard practice is to measure width brick to brick, from the inside edge of the masonry or siding on one side to the inside edge on the other, rather than from the existing window frame itself. This accounts for the true structural opening rather than the current window’s trim, which may not reflect the actual space available.
It’s important to measure at multiple points, top, middle, and bottom of the opening, since older openings are rarely perfectly uniform from top to bottom.
Measuring Height & the Fitting Tolerance
Height is measured the same way, from the sill to the head of the opening, again checking at a few points across the width rather than relying on a single measurement. Once the raw height and width are recorded, it’s standard practice to subtract about 10 millimeters from each final dimension.
This small adjustment leaves enough tolerance for the window to be fitted properly during installation, without being so tight that it can’t be leveled and shimmed correctly, or so loose that it leaves excessive gaps to seal. Our full lineup of replacement windows is built to these precise tolerances for a proper fit.
Why This Is a Job for a Professional
While the measuring process itself isn’t complicated in concept, getting it right consistently, especially across multiple points and irregular older openings, benefits from experience. A professional measurement also catches problems early: a frame that’s out of square, sill damage, or an opening that’s settled unevenly, all details that affect whether a standard or custom window is the right call.
Our energy-efficient window solutions team takes precise measurements as a standard part of every project, and our Professional Window Installation guide covers more of what separates a professional installation from a DIY or unqualified one.
Getting Accurate Window Measurements
Precise measurements, brick to brick for width, sill to head for height, and a small fitting tolerance subtracted from both, are what make a replacement window fit and seal the way it’s supposed to. If you’re comparing installers for an upcoming project, our Window Contractors Utah guide covers what else to check before hiring.
Ready for accurate, professional window measurements? Schedule a free consultation with our Salt Lake City team for a free quote.