Rectangle Calculator for Area, Perimeter, Diagonal and Side Lengths

Updated By Unit Conversion Plus

Solve a rectangle from two known measurements and see its area, perimeter and diagonal.

Known measurements

Rectangle formulas

A = lw · P = 2(l + w) · d = √(l² + w²)

Solving from area or perimeter

If area and length are known, width is A ÷ l. If perimeter and length are known, width is P ÷ 2 − l.

Solving from a diagonal

With the diagonal and one side, the other side follows from the Pythagorean theorem. The diagonal must be longer than the known side.

Frequently asked questions

Is a square a rectangle?

Yes. A square is a rectangle whose four sides have equal length.

Does changing the unit convert the inputs?

No. Enter both measurements in the same unit.