Rectangle Area Calculator
Find area, perimeter, and diagonal of rectangles and squares. Enter length and width to get comprehensive geometric measurements instantly.
Result
- Area
- 0 square units
- Perimeter
- 0 units
- Diagonal
- 0 units
Formula & Guide
Formulas
A
Area
Area = Length × Width
Multiply length by width
P
Perimeter
Perimeter = 2 × (Length + Width)
Add length and width, then multiply by 2
D
Diagonal
Diagonal = √(Length² + Width²)
Pythagorean theorem
Formula Variables
Length
Length
The longer side (or any side) of the rectangle
Width
Width
The shorter side (or adjacent side) of the rectangle
Area
Area
The amount of space inside the rectangle, measured in square units
Perimeter
Perimeter
The total distance around the rectangle
Step-by-Step Scenario
Example Scenario
Length
10 units
Width
5 units
1
Calculate Area
- Area = Length × Width
- Area = 10 × 5
2
Calculate Perimeter
- Perimeter = 2 × (Length + Width)
- Perimeter = 2 × (10 + 5)
- Perimeter = 2 × 15
3
Calculate Diagonal
- Diagonal = √(Length² + Width²)
- Diagonal = √(10² + 5²)
- Diagonal = √(100 + 25) = √125
Additional Examples
Square
Length: 6 units
Width: 6 units
Area
6 × 6 = 36 square units
Perimeter
2 × (6 + 6) = 24 units
Large Rectangle
Length: 15 units
Width: 8 units
Area
15 × 8 = 120 square units
Perimeter
2 × (15 + 8) = 46 units
Characteristics of Rectangles
Simple Formula
Rectangle area uses the simplest geometric formula: just multiply length by width. This makes it easy to calculate and understand.
Square as Special Case
A square is a rectangle with equal sides. When length equals width, you have a square, and the formulas still apply.
Practical Applications
Used extensively in construction, architecture, flooring, painting, landscaping, and any field involving rectangular spaces.
Right Angles
All rectangles have four right angles (90 degrees), making them perfect for construction and design applications.
Important Notes
- Length and width can be interchanged - the area remains the same regardless of which dimension is called length or width.
- For squares, enter the same value for both length and width. The formulas work the same way.
- Area is always expressed in square units (e.g., square meters, square feet) based on the units of the input measurements.
- The diagonal divides the rectangle into two congruent right triangles, which is why the Pythagorean theorem applies.
- Perimeter represents the total distance around the rectangle, useful for fencing, framing, and border calculations.
Frequently Asked Questions
Find answers to common questions about rectangle calculations.
Rectangle area is calculated by multiplying length by width: Area = Length × Width. For example, a rectangle with length 10 and width 5 has an area of 50 square units.
A square is a special type of rectangle where all four sides are equal. Both use the same area formula (length × width), but in a square, length equals width.
The perimeter is calculated by adding all four sides: Perimeter = 2 × (Length + Width). This formula works because opposite sides are equal in a rectangle.
The diagonal can be found using the Pythagorean theorem: Diagonal = √(Length² + Width²). This creates a right triangle with the diagonal as the hypotenuse.
You can use any units (meters, feet, inches, etc.) as long as all measurements use the same unit. Area will be in square units, and perimeter/diagonal will be in the same unit as the sides.
Yes, this calculator works perfectly for squares. Just enter the same value for both length and width. The formulas remain the same, but all sides will be equal.