Perimeter calculator

Add the side lengths of a closed polygon to find its perimeter.

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Consecutive side lengths

Answer

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Add the side lengths of a closed polygon to find its perimeter.

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Precision and calculation record

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Rounding changes displayed numbers, not the calculation. Text, fractions, matrices and CSV schedules keep their own formatting. Automatic keeps up to 12 significant digits, with money shown to cents where applicable.

Saved scenario

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Formula and assumptions

Enter each boundary segment once in one unit. Checks the polygon side inequality, but lengths alone cannot determine area or establish the actual shape.

In a list, use spaces, new lines, semicolons, or commas followed by a space. A comma between groups of three digits is a thousands separator.

Automatic precision shows numbers to 12 significant digits. Thousands separators such as 1,000 are accepted; use a dot for decimals.

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Updated 2026-09-26

Using Perimeter calculator

Add the side lengths of a closed polygon to find its perimeter.

Enter each boundary segment once in one unit. Checks the polygon side inequality, but lengths alone cannot determine area or establish the actual shape.

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A worked example

Example inputs: consecutive side lengths = 3 4 5. Polygon perimeter = 12.

Before you use the result

Enter each boundary segment once in one unit. Checks the polygon side inequality, but lengths alone cannot determine area or establish the actual shape.

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ToolOctopus. “Perimeter calculator.” Updated 2026-09-26. https://tooloctopus.com/perimeter-calculator.

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