Perimeter Calculator
Calculate the perimeter of rectangles, squares, triangles, circles, trapezoids, parallelograms, and ellipses. Enter your dimensions and get instant results with formulas and a visual breakdown. Perfect for students, teachers, and professionals.
What Is Perimeter?
Perimeter is the total distance around the outside of a two-dimensional shape. It is measured in linear units, such as meters (m), feet (ft), or centimeters (cm). Perimeter is a fundamental concept in geometry with many real-world applications — from measuring the length of fencing needed for a yard to calculating the trim required for a room.
This calculator supports seven common shapes: rectangles, squares, triangles, circles (where the perimeter is called the circumference), trapezoids, parallelograms, and ellipses. Each shape has a specific formula that uses its dimensions to calculate the perimeter.
How Does the Perimeter Calculator Work?
The calculator uses standard geometric formulas for each shape:
Rectangle: Perimeter = 2 × (Length + Width)
Square: Perimeter = 4 × Side
Triangle: Perimeter = Side A + Side B + Side C
Circle (Circumference): Perimeter = 2 × π × Radius
Trapezoid: Perimeter = Base₁ + Base₂ + Leg₁ + Leg₂
Parallelogram: Perimeter = 2 × (Side A + Side B)
Ellipse (Approx): Perimeter ≈ 2π × √((a² + b²) / 2)
Simply select a shape, enter the required dimensions, and the calculator will instantly compute the perimeter. You can switch between metric and imperial units, and choose how many decimal places to display.
Why Use This Perimeter Calculator?
- Seven Shapes: Supports rectangles, squares, triangles, circles, trapezoids, parallelograms, and ellipses.
- Unit Flexibility: Switch between metric (meters, centimeters) and imperial (feet, inches).
- Formula Display: See the formula used and the step-by-step calculation.
- Visual Comparison: A bar chart shows the relative dimensions of the shape.
- Free & Private: No registration, no data storage.
Real-World Applications of Perimeter
- Construction: Measuring the length of fencing, baseboards, or crown molding.
- Landscaping: Determining the amount of edging material for gardens or lawns.
- Sports: Measuring running track lengths, field perimeters, and court dimensions.
- Design: Sizing picture frames, borders, and decorative trims.
- Education: Learning geometry and solving math problems.
❓ Perimeter Calculator FAQ
What is perimeter?
Perimeter is the total distance around the outside of a two-dimensional shape. It is measured in linear units (e.g., m, ft, cm).
How do I calculate the perimeter of a rectangle?
Add the length and width, then multiply by 2. Formula: P = 2 × (L + W). For example, a rectangle with length 10 m and width 6 m has a perimeter of 32 m.
How do I calculate the perimeter of a square?
Multiply the side length by 4. Formula: P = 4 × s. For example, a square with side 8 m has a perimeter of 32 m.
How do I calculate the perimeter of a triangle?
Add all three sides. Formula: P = a + b + c. For example, a triangle with sides 8, 10, and 12 m has a perimeter of 30 m.
What is the perimeter of a circle called?
The perimeter of a circle is called the circumference. Formula: C = 2 × π × r. For example, a circle with radius 5 m has a circumference of 31.42 m.
How do I calculate the perimeter of a trapezoid?
Add all four sides. Formula: P = b₁ + b₂ + l₁ + l₂. For example, a trapezoid with bases 12 and 8 m and legs 5 and 6 m has a perimeter of 31 m.
How do I calculate the perimeter of a parallelogram?
Add the two side lengths and multiply by 2. Formula: P = 2 × (a + b). For example, a parallelogram with sides 10 and 6 m has a perimeter of 32 m.
How do I calculate the perimeter of an ellipse?
An exact formula is complex. This calculator uses the approximation: P ≈ 2π × √((a² + b²) / 2), where a and b are the semi-major and semi-minor axes.
What is the difference between perimeter and area?
Perimeter measures the distance around the outside of a shape (1D). Area measures the space inside a shape (2D). They are different measurements used for different purposes.
How do I convert meters to feet for perimeter?
Multiply meters by 3.28084 to get feet. The calculator automatically converts between units.
What is the perimeter of a circle with diameter 10?
Radius = Diameter/2 = 5. Circumference = 2 × π × 5 = 31.42 units. The calculator can use either radius or diameter.
What is the perimeter of a triangle with sides 5, 7, and 9?
Perimeter = 5 + 7 + 9 = 21 units.
What is the perimeter of a rectangle with length 15 and width 10?
Perimeter = 2 × (15 + 10) = 2 × 25 = 50 units.
What is the perimeter of a square with side 12?
Perimeter = 4 × 12 = 48 units.
What is the perimeter of a trapezoid with bases 20 and 14 and legs 10 and 8?
Perimeter = 20 + 14 + 10 + 8 = 52 units.
What is the perimeter of a parallelogram with sides 18 and 12?
Perimeter = 2 × (18 + 12) = 2 × 30 = 60 units.
What is the perimeter of an ellipse with semi-major axis 10 and semi-minor axis 6?
Using the approximation: P ≈ 2π × √((10² + 6²) / 2) = 2π × √((100 + 36) / 2) = 2π × √(68) ≈ 51.81 units.
What units can I use for perimeter?
Perimeter can be measured in meters (m), centimeters (cm), feet (ft), inches (in), and many other linear units. This calculator supports metric and imperial systems.
How do I calculate the perimeter of an irregular shape?
For irregular shapes, measure each side and add them together. This calculator focuses on seven common regular shapes.
What is π (Pi) in perimeter calculations?
π (Pi) is a mathematical constant approximately equal to 3.14159. It is used in formulas for circles, ellipses, and other curved shapes. The calculator uses π to compute circumferences and ellipse perimeters.
How do I calculate the perimeter of a room for baseboard?
Measure the length and width of the room. Use the rectangle formula: P = 2 × (L + W). For irregular rooms, measure each wall and add them together. Use this calculator with the appropriate shape.