Rectangle Calculator
Calculate rectangle area, perimeter and diagonal.
How to Use the Rectangle Calculator
Enter the rectangle length and width to calculate area, perimeter and diagonal length.
Practical Example
A rectangle that is 12 units long and 5 units wide has an area of 60 square units and a perimeter of 34 units.
Factors That Affect the Result
The result depends on using the same unit for both dimensions and entering accurate measurements. The diagonal is calculated from the Pythagorean relationship.
Frequently Asked Questions
How is rectangle area calculated?
Multiply length by width.
How is perimeter calculated?
Add length and width, then multiply by two.
Can I use any unit?
Yes, as long as both dimensions use the same unit.
Related Tools
Understanding Rectangle Measurements
A rectangle’s area is length × width, perimeter is 2(length + width), and diagonal is found with √(length² + width²). These formulas assume four right angles and opposite sides of equal length.
Use the same unit for both dimensions before calculating. For rooms, panels or plots that are not perfectly rectangular, divide the space into simpler sections or measure diagonals to check squareness. Material ordering may also require a waste allowance beyond the ideal geometric area.