Rectangle Calculator

Calculate perimeter and area from dimensions, or solve reverse problems to find unknown measurements. Perfect for construction, flooring, and fencing projects.

Calculate perimeter, area, and solve reverse problems

Calculation Mode

Length (a)

Width (b)

Unit

Real-World Applications

Room Flooring

Calculate flooring area needed for a rectangular room

Length: 5m, Width: 4m → Area: 20m²

Garden Fencing

Calculate fence length needed around a rectangular garden

Length: 8m, Width: 6m → Perimeter: 28m

Wall-Adjacent Fencing

For fencing against a wall, subtract the wall side from perimeter

If one side is against wall: 28m - 8m = 20m fence needed

Rectangle Properties & Common Mistakes

✅ Key Properties:

• Four right angles (90°)
• Opposite sides are parallel and equal
• Diagonals are equal and bisect each other
• Perimeter = 2 × (length + width)
• Area = length × width

❌ Common Mistakes:

• Confusing which dimension is length vs width
• Using length + width for perimeter (forgetting ×2)
• In wall-adjacent problems, not subtracting wall side
• Mixing up area and perimeter units (cm² vs cm)

Calculator Features

Basic Calculations

Enter length and width to calculate perimeter and area

P = 2(l + w), A = l × w

Reverse Problem Solving

Find unknown dimensions from known perimeter or area

w = (P ÷ 2) - l, l = A ÷ w

Real-World Applications

Perfect for flooring, fencing, and construction calculations

Includes wall-adjacent scenarios

How to Use the Rectangle Calculator

Basic Calculation (Length & Width → Results)

1Select "Basic" calculation mode
2Enter the length and width values
3Choose your unit of measurement
4Click "Calculate" to see perimeter and area

Reverse Problems

Find Width from Perimeter

When you know the length and perimeter, calculate the width using: Width = (Perimeter ÷ 2) - Length

Find Length from Area

When you know the width and area, calculate the length using: Length = Area ÷ Width

Related Tools & Learning

Rectangle Properties

Learn about rectangle characteristics and formulas

Square Calculator

Calculate square dimensions (special case of rectangle)

Parallelogram Calculator

Calculate parallelogram area and perimeter