Rectangle Calculator

Calculate area, perimeter, diagonal, and all properties of rectangles with step-by-step solutions

Rectangle Properties

Area
0
square units
Perimeter
0
linear units
Diagonal
0
linear units
Aspect Ratio
0
length:width
Rectangle Visualization
Length Width Diagonal
Area Formula: A = l × w
Perimeter: P = 2(l + w)
Diagonal: d = √(l² + w²)

Rectangle Properties

Area
0
square units
Length
0
linear units
Perimeter
0
linear units
Diagonal
0
linear units
Rectangle Visualization
A
Length Formula: l = A ÷ w
Perimeter: P = 2(l + w)
Diagonal: d = √(l² + w²)

Rectangle Properties

Perimeter
0
linear units
Length
0
linear units
Area
0
square units
Diagonal
0
linear units
Rectangle Visualization
P
Length Formula: l = (P ÷ 2) - w
Area: A = l × w
Diagonal: d = √(l² + w²)

Rectangle Properties

Diagonal
0
linear units
Length
0
linear units
Area
0
square units
Perimeter
0
linear units
Rectangle Visualization
d
Length Formula: l = √(d² - w²)
Area: A = l × w
Perimeter: P = 2(l + w)

How to Use the Rectangle Calculator

Our comprehensive rectangle calculator offers four different calculation modes to find all rectangle properties from any known measurements:

📏 Length & Width Mode

Enter both dimensions to calculate area (A = l×w), perimeter (P = 2(l+w)), diagonal (d = √(l²+w²)), and aspect ratio. Most common calculation method.

📐 Area & Width Mode

Input the area and width to find the length (l = A÷w) and all other properties. Perfect when you know the surface area and one dimension.

🔄 Perimeter & Width Mode

Enter the perimeter and width to calculate length (l = (P÷2)-w), area, and diagonal. Useful for fencing or boundary calculations.

📐 Diagonal & Width Mode

Input the diagonal and width to find length using Pythagorean theorem (l = √(d²-w²)). Great for construction and design applications.

📊 Visual Features

• Interactive Rectangle Diagrams: See your rectangle with proper proportions and labeled dimensions
• Formula Display: All relevant formulas shown for educational value
• Aspect Ratio: Length-to-width ratio for design and proportion analysis
• Real-time Results: Instant calculations with high precision

💡 Pro Tips

• All measurements should use the same units
• Results are precise to 4 decimal places
• Visual diagrams help understand relationships between properties
• Use aspect ratio to determine if rectangle is square (1:1) or elongated
• Perfect for construction, design, gardening, and academic applications

Frequently Asked Questions

Conventionally, length refers to the longer side and width to the shorter side of a rectangle. However, for calculation purposes, you can assign either dimension as length or width - the mathematical results remain the same.
The diagonal is calculated using the Pythagorean theorem: d = √(length² + width²). This represents the straight-line distance from one corner to the opposite corner of the rectangle.
Aspect ratio is the relationship between length and width (length:width). It's important in design, photography, and screen dimensions. A 1:1 ratio means the rectangle is actually a square, while 16:9 is common for widescreen displays.
Choose based on what measurements you know: use Length & Width if you can measure both sides, Area & Width if you know the surface area, Perimeter & Width for boundary calculations, or Diagonal & Width for construction applications.
Yes! Use any unit system (meters, feet, inches, centimeters, etc.), but keep all inputs in the same unit. Results will be in corresponding units: linear units for dimensions, square units for area.