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Geometry

Circle Circumference Calculator

Find the distance around the edge of a circle.

Let’s calculate.

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Your result
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Rounded to up to 2 decimal places.

Measurement units

Changing the input unit also selects its matching result unit. Choose another result unit to convert the answer. Input numbers stay unchanged.

SI prefixes and selected international / customary units. Coverage: SI and selected current customary units. Historical units are excluded.

See what you’re calculating

r
Circumference = 2 × π × radius

Find the distance around the edge of a circle.

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THE IDEA, SIMPLY

How it works

Find the distance around the edge of a circle.

FORMULA

Circumference = 2 × π × radius

A worked example

Radius 5 m gives circumference ≈ 31.4159 m.

Formula & detailed explanation

Radius must be nonnegative. Pi is evaluated with Decimal arithmetic.

Calculations use decimal arithmetic with 40 significant digits internally. Choose 0–8 decimal places for the displayed result. Trailing zeros are omitted. Rounding affects only the displayed and copied result; very small values may round to zero. Accepted inputs have up to 100 characters and magnitudes from 10⁻¹⁰⁰ to 10¹⁰⁰, plus zero.

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