Motion Windows Radius Measurement Tool

Use our printable radius gauge to determine whether the rounded corners of your window’s rough opening have a 2½-inch or 3-inch radius.

Download & Print the Radius Gauge

Download the gauge and print at Actual Size (100%). Before cutting it out, measure from arrow to arrow. The measurement must be exactly 5½ inches.

If the measurement is incorrect, turn off “Fit to Page” or other scaling options and print again. Word is the preferred format.

Download Word Template — Preferred
Download PDF Template

Cut carefully along the gauge’s outer outline after verifying its printed size.

How to Measure Your Corner Radius

1

Expose the Rough Opening

Remove the interior trim ring or remove the window completely so you can see the actual opening cut into the wall. Do not measure the window frame, glass, or trim ring.

2

Extend Both Straight Edges

Use a straightedge to follow the two straight sides next to the rounded corner. Imagine or mark where those lines would continue until they intersect.

3

Position the Radius Gauge

Move and rotate the gauge so the 2½-inch or 3-inch curved edge touches both extended lines. Use the arrow on the selected radius side to point toward the corner where the lines intersect.

4

Check the Curve

Compare the gauge’s curved edge with the actual rounded cutout. The curves should closely follow each other. If there is a visible gap or overlap, try the other radius.

Compare Correct and Incorrect Fits

These examples use the actual Peninsula Glass radius gauge. The blue line shows the rough opening; the black outline shows the gauge. The dashed lines extend the straight edges of the opening.

3-Inch Radius

Correct 3-inch radius: gauge curve follows the blue rough-opening curve while touching both extended straight lines.
✓ Correct FitThe 3-inch curve closely follows the rough opening.
Incorrect 3-inch radius: blue rough-opening curve does not follow the gauge's edge.
✕ Incorrect FitThe gauge and opening curves do not match.

2½-Inch Radius

Correct 2-and-a-half-inch radius: gauge curve follows the blue rough-opening curve while touching both extended straight lines.
✓ Correct FitThe 2½-inch curve closely follows the rough opening.
Incorrect 2-and-a-half-inch radius: blue rough-opening curve does not follow the gauge's edge.
✕ Incorrect FitThe gauge and opening curves do not match.

Important: The radius must be confirmed before we can proceed with a window order, although it is not required for an initial quotation. Rough-cut openings may not match perfectly; compare the overall shape of the curve.

Additional Measurement Tips

Do I need to measure every window?

Often, windows on the same vehicle share a corner radius. However, check any window that looks or functions differently, especially door windows and emergency egress windows.

What if neither radius matches?

If neither the 2½-inch nor 3-inch side closely follows your rough opening, contact Motion Windows before ordering. We may ask you to send a physical pattern so we can draw the opening in CAD and discuss replacement options.