Calculating perimeter is essential for construction, crafting, landscaping, and education. Our free perimeter calculator computes the distance around any geometric shape - rectangles, squares, triangles, circles, polygons, and more. Whether you're figuring out how much fencing you need, planning picture frames, or solving geometry homework, get instant results with clear formulas and step-by-step explanations.
Perimeter is the total length of the boundary enclosing a two-dimensional shape. For polygons (shapes with straight sides), it's the sum of all side lengths. For circles, it's called circumference. Think of perimeter as the distance you would travel walking along the outside edge of a shape. Units are linear measurements (feet, meters, centimeters, etc.). Perimeter differs from area - while area measures the space inside, perimeter measures the distance around the outside.
Calculate perimeter for multiple shapes: rectangle, square, triangle, circle, polygon, Support for regular and irregular polygons, Circle circumference calculated with π, Step-by-step solutions showing formulas, Handles any units of measurement, Works with decimals and fractions, Mobile-friendly responsive design, No registration required, Copy results easily, Educational explanations included.
Select your shape type from the menu or enter dimensions directly. The calculator applies the appropriate formula based on shape: Rectangle: P = 2(length + width), Square: P = 4 × side, Triangle: P = side₁ + side₂ + side₃, Circle: C = 2πr or πd, Polygon: P = sum of all sides. For each calculation, the tool displays the formula used and shows step-by-step work. You can enter measurements in any unit (feet, meters, etc.) as long as you're consistent.
Construction and Landscaping - Fencing for gardens, yards, and fields. Edging for lawns and flower beds. Planning walkways and paths. Determining material needs for borders. Framing and Crafts - Picture frames and photo mounts. Mirror and artwork framing. Baseboards and trim for rooms. Border materials for crafts. Manufacturing - Cutting stock for frames. Planning packaging dimensions. Material estimation. Education - Geometry homework and tests. Teaching perimeter concepts. Mathematical modeling. Property Management - Property boundary surveys. Land perimeter calculations. Fence installation quotes.
Manual perimeter calculations are simple for basic shapes but can become complex with irregular polygons or multi-step problems. Our calculator eliminates arithmetic errors, handles multiple shapes efficiently, provides instant results, shows the formula and steps used, ensures accuracy for materials estimation, works with any measurement units, and serves as a learning tool for students. Getting exact measurements prevents over-ordering or shortages of materials.
Homeowners doing DIY projects or landscaping, Gardeners planning fences and borders, Contractors estimating materials, Students learning geometry, Teachers creating examples, Crafters and artists framing work, Manufacturers planning cuts, Landscapers quoting jobs, Interior designers planning trim, Anyone needing distance-around measurements.
Select your shape type from the dropdown or shape selector, Enter the required dimensions (lengths of sides, radius, etc.), Ensure all measurements use the same units, Click Calculate, Review the perimeter result, Check the formula and calculation steps shown, Copy the answer for your records or project planning.
Always use consistent units - don't mix inches with feet or centimeters with meters, Double-check measurements before calculating, For fences add 5-10% extra for gates and posts when ordering materials, Remember Circumference specifically for circles (not perimeter), For irregular shapes, carefully measure each side, Draw a diagram to ensure you haven't missed any sides, Round up when purchasing materials to ensure you have enough.
Calculator handles standard geometric shapes, Irregular curved shapes may require approximation, Extremely large measurements may display in scientific notation, Composite shapes (combined shapes) require calculating outer boundary only, Calculator assumes closed shapes with well-defined boundaries.
Perimeter is the total distance around the outer boundary of a two-dimensional shape. It's the sum of the lengths of all sides or edges. For circles, it's called circumference. Example: Rectangle 5m × 3m has perimeter = 2(5+3) = 16m. Square with side 4cm has perimeter = 4×4 = 16cm. Triangle with sides 3, 4, 5 has perimeter = 3+4+5 = 12 units.
Use the formula: P = 2(l + w) where l = length, w = width. Or P = 2l + 2w. Example: Rectangle with length 8 ft and width 5 ft. P = 2(8 + 5) = 2(13) = 26 ft. Or: 2×8 + 2×5 = 16 + 10 = 26 ft. The perimeter represents the distance around the rectangle - imagine walking along all edges.
P = 4 × s where s = side length. Since all four sides are equal, simply multiply one side by 4. Example: Square with side 6 cm. P = 4 × 6 = 24 cm. If garden is square with 10 ft sides, fence needed = 4 × 10 = 40 ft.
Add all three sides: P = a + b + c. Example: Triangle with sides 7, 8, 9 inches. P = 7 + 8 + 9 = 24 inches. For equilateral triangle: P = 3 × side. For isosceles: P = 2 × equal side + base. For right triangles, can use Pythagorean theorem to find missing side first.
Perimeter applies to polygons (shapes with straight sides): rectangles, triangles, squares, pentagons, etc. Circumference applies specifically to circles and circular shapes. Formulas: Perimeter = sum of all sides. Circumference C = 2πr or C = πd where r = radius, d = diameter. Both measure distance around a shape, just different terminology.
For any polygon, perimeter = sum of all sides. Simply add up every side length. Example: Irregular pentagon with sides 3, 5, 4, 6, 7 cm. P = 3 + 5 + 4 + 6 + 7 = 25 cm. For shapes with curved sides, you may need calculus or approximation. For composite shapes (multiple shapes combined), find outer boundary only.
Construction: Fencing for gardens, yards, fields. Framing: Picture frames, mirrors, artwork. Borders: Edging for lawns, paths, landscaping. Construction materials: Baseboards, trim, molding. Sports: Track around fields and courts. Security: Perimeter security systems. Manufacturing: Cutting frames, borders, trim pieces. Real estate: Property boundary measurements.
Perimeter (linear measurement) and area (square measurement) are different concepts. Two shapes can have same perimeter but different areas, or same area but different perimeters. Example: Rectangle 4×4 (P=16, A=16) vs 7×1 (P=16, A=7). For given perimeter, square maximizes area. For given area, circle minimizes perimeter.