Rectangle Diagonal Calculator
Compute the diagonal of any rectangle given width and height. Includes a squaring verification feature for construction framing.
About
Square corners are a prerequisite for structural stability in framing, decking, and screen manufacturing. The diagonal measurement acts as the control variable; if the measured diagonal matches the calculated hypotenuse, the angle formed by width and height is exactly 90 degrees. This utility computes that critical length.
Deviations in diagonal length indicate a "racked" frame (parallelogram shape). Correcting this before fastening sheathing or drywall prevents costly rework. This tool applies the Pythagorean theorem to two non-equal sides.
Formulas
The diagonal d cuts the rectangle into two right-angled triangles. We solve for the hypotenuse:
Reference Data
| Width (w) | Height (h) | Diagonal (d) | Common Use |
|---|---|---|---|
| 3 | 4 | 5 | 3-4-5 Triangle Rule |
| 5 | 12 | 13 | Construction Layout |
| 8 | 15 | 17 | Foundation Check |
| 9 | 16 | 18.357 | 16:9 Aspect Ratio |
| 16 | 24 | 28.844 | Stud Spacing |
| 60 | 80 | 100 | Large Frame |
| 1920 | 1080 | 2202.9 | FHD Screen (px) |
| 3840 | 2160 | 4405.8 | 4K Screen (px) |