Work out the diagonal of a rectangle when you need a corner-to-corner distance for screens, layouts, framing checks, or geometry.
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diagonal = sqrt(length^2 + width^2)The diagonal forms the hypotenuse of a right triangle built from the two side lengths.
This is the same principle used in 3-4-5 layout checks.
Open this calculator for cases where a small arithmetic slip would otherwise force a full restart around cube face diagonal.
Next: rectangle area.
Calculate rectangle perimeter when you need border length for trim, fencing, framing, edging, or basic geometry problems.
Because a rectangle diagonal creates a right triangle with the rectangle sides.
Yes, if you know the visible width and height of the display area.
Informational calculator only. Verify important outputs independently before legal, tax, medical, engineering, safety-critical, contractual, employment, or compliance use.