Area of a Rectangle Calculator FAQs
What is the formula for the area of a rectangle?
The basic rectangle area formula is A = l x w, where l is the length and w is the width.
How do I calculate the area of a rectangle from length and width?
Multiply the length by the width. For example, if the length is 10 cm and the width is 6 cm, the area is 60 cm^2.
Can I find the area of a rectangle from perimeter and one side?
Yes. If you know one side s and the perimeter P, first find the other side as P/2 - s, then calculate the area with A = s(P/2 - s). This is the standard way to solve rectangle area from perimeter and side.
Can I calculate the area of a rectangle from diagonal and one side?
Yes. If you know one side s and the diagonal d, use the Pythagorean theorem to find the other side, then calculate the area with A = s x sqrt(d^2 - s^2).
Can I find rectangle side lengths from the area?
Yes. Switch the active input, enter the area and the required known value, and the calculator will solve the missing dimensions. In perimeter and diagonal modes, it shows the shorter side as Side and the longer side as Length.
What if I know the area and perimeter of a rectangle?
The calculator can solve the two valid side lengths from the area and perimeter using the reverse formula s = (P ± sqrt(P^2 - 16A)) / 4. It shows the shorter result as Side and the longer result as Length.
What if I know the area and the diagonal of a rectangle?
The calculator can solve the two valid side lengths from the area and diagonal using the reverse diagonal relation. It shows the shorter result as Side and the longer result as Length.
