Rectangle Area Calculator
Area, Perimeter & Diagonal ⚡
Calculate the area, perimeter, and diagonal of any rectangle or square instantly.
Quick Examples
Rectangle Formulas
Area: A = length × width
Perimeter: P = 2 × (length + width)
Diagonal: d = √(length² + width²)
A square is a special rectangle where length = width.
Related Calculators
Frequently Asked Questions
What is the difference between area and perimeter?
Area is the space inside the rectangle, measured in square units. Perimeter is the total distance around the outside, measured in the same units as the length and width.
How do I find the diagonal of a rectangle?
Use Pythagoras' theorem — the diagonal is the hypotenuse of a right triangle formed by the length and width. Diagonal = √(length² + width²).
What units should I use?
Any units — cm, m, inches, feet. Just be consistent. If length is in metres, area will be in square metres (m²) and perimeter in metres (m).