Rectangle & Square Calculator - Free Online Area, Perimeter & Diagonal Calculator
Rectangle & Square Calculator
Calculate area, perimeter, and diagonal of rectangles and squares. Enter any two known values to find all properties.
How to use this calculator
📐 How to Use the Rectangle & Square Calculator
- Choose between Rectangle or Square using the tabs
- For rectangles: Enter both length and width
- For squares: Enter the side length
- Select your preferred unit of measurement
- Click the Calculate button to see area, perimeter, and diagonal
📏 Rectangle & Square Formulas
Rectangle Formulas:
- Area = length × width
- Perimeter = 2(length + width)
- Diagonal = √(length² + width²)
Square Formulas:
- Area = side²
- Perimeter = 4 × side
- Diagonal = side × √2
🌟 Real-World Examples
Example 1: Room Flooring
A room measuring 4m × 5m has an area of 20m² and needs 18m of baseboard (perimeter).
Example 2: Garden Plot
A square garden with 3m sides has an area of 9m² and requires 12m of fencing.
Example 3: TV Screen Size
A 16:9 TV with 80cm width and 45cm height has a diagonal of about 91.8cm (36 inches).
💡 Pro Tips
- • A square is a special rectangle where all sides are equal
- • The diagonal divides a rectangle into two right triangles
- • For squares, the diagonal is always side × 1.414 (√2)
- • Area is always in square units (m², ft², etc.)
- • The golden rectangle has an aspect ratio of approximately 1.618:1
⚠️ Common Mistakes to Avoid
- • Don't confuse perimeter (distance around) with area (space inside)
- • Remember that area uses square units, not linear units
- • Ensure length and width are in the same units before calculating
- • The diagonal is NOT the sum of two sides
- • For irregular quadrilaterals, these formulas don't apply
About this calculator
Calculate rectangle and square area, perimeter, and diagonal length instantly. Free online calculator with visual diagrams and step-by-step solutions.
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