Diagonal Of A Rectangle Calculator

Work out diagonal of a rectangle instantly with clear inputs, formula shown and shareable results.

About Diagonal Of A Rectangle Calculator

A rectangle's diagonal closes a right triangle on its length and width, so Pythagoras gives d = √(l² + w²). The diagonal's angle to the long side is arctan(w/l).

Formulas

Diagonal

d = √(l² + w²)

Diagonal angle

θ = arctan(w / l)

Worked example

With the default values below, Diagonal Of A Rectangle Calculator returns Diagonal of 10.0000. Change any input above and every figure here is recalculated in your browser.

Inputs used

Lengthminimum 0: 8
Widthminimum 0: 6

Results

Diagonal: 10.0000
Area: 48.0000
Perimeter: 28.0000
Angle the diagonal makes with the length: 36.8699 °

Step by step

1Values used
2Diagonal
3Diagonal angle
4Diagonal= 10.0000
5Area= 48.0000
6Perimeter= 28.0000
7Angle the diagonal makes with the length= 36.8699 °

Assumptions and limits

The result is derived only from the 2 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

8 by 6 gives what diagonal?

√(64 + 36) = 10 exactly — the 6-8-10 Pythagorean triple.

Is this how TV screen size is quoted?

Yes. A television's stated size is its screen diagonal, so the same formula converts between diagonal and width/height.