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Regular Decagon Calculator

Result

Calculated result 20 Based on the values entered.
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Regular Decagon Calculator Calculate area and perimeter of a regular decagon. — free online calculator.

Formula

Area = 2.5s²√(5+2√5); Perimeter = 10s
  • Regular Decagon Calculator calculates its result from S. It uses the formula Area = 2.5s²√(5+2√5); Perimeter = 10s. Change any input to recalculate the result instantly.
  • The main inputs are S. Enter them in the units and format shown in the calculator.
  • Keep comparable quantities in compatible units whenever the formula combines or compares them.
  • Changing any input above recalculates the result with the same calculation engine used by this page.

Example: Regular Decagon

Inputs
  • S: 2

Using S = 2, the calculated result is 20.

Sample result: Calculating…

Frequently asked questions

What does the Regular Decagon calculate?

Regular Decagon Calculator Calculate area and perimeter of a regular decagon. — free online calculator.

Which values should I enter?

Enter S using the units and format shown beside each field.

What formula does this calculator use?

The calculator uses the following relationship: Area = 2.5s²√(5+2√5); Perimeter = 10s.

Why might my result differ from another source?

Results can differ when another source uses different units, rounding rules, conventions or assumptions. Compare the inputs and definitions before comparing results.

Does the result update automatically?

Yes. Changing an input updates the result using the same calculation engine shown on this page.

Page information

Updated: October 7, 2026