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Ellipse area and semiaxes: Major semiaxis Calculator

Ellipse area and semiaxes: Calculate major semiaxis from Area, Minor semiaxis. Check the formula, input units and worked result on this page.

Enter your values

cm²
Formula symbol: A. Required unit: cm². Must be greater than zero.
cm
Formula symbol: b. Required unit: cm. Half the full dimension in that direction. Must be greater than zero.

Use a decimal point, without thousands separators.

Lengths use cm, areas cm² and volumes cm³ on one consistent scale. The positive real branch is selected; the supplied quantities must describe the stated shape.
Example result
Major semiaxis
5 cm

The initial result uses the example values. Enter your own values and calculate again.

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How it works

Semiaxes are half the full widths. With eccentricity, the minor semiaxis is a√(1−e²). This form solves for major semiaxis; enter the known quantities in Area, Minor semiaxis.

Inputs and units
Ellipse area and semiaxes: Major semiaxis Calculator · Inputs and units
InputExample valueWhat to enter
Area47.12388980384689 cm²Formula symbol: A. Required unit: cm². Must be greater than zero.
Minor semiaxis3 cmFormula symbol: b. Required unit: cm. Half the full dimension in that direction. Must be greater than zero.
a = A / (πb)

Worked example

Show example inputs and results

This example is generated by the same calculation engine using the starting values in the form. Your own inputs produce your own result.

Area
47.12388980384689 cm²
Minor semiaxis
3 cm

Complete example results

Major semiaxis
5 cm

Reading the result

The result solves for major semiaxis from the entered quantities. Check the result unit and the formula conditions before using it.

Questions and answers

Can I use the example values for my own calculation?

The example values illustrate the calculation. Replace every input with your own information, especially dates, rates and the selected operation.

When can I use the major semiaxis result?

Lengths use cm, areas cm² and volumes cm³ on one consistent scale. The positive real branch is selected; the supplied quantities must describe the stated shape.

Why are some results rounded?

Results display up to 8 decimal places. Calculations use the unrounded values; very small values use scientific notation. JavaScript floating-point arithmetic can introduce tiny rounding differences.

Are my inputs sent to a server?

The calculator processes inputs in your browser. Its code does not send your values to a server.

Method sources: openstax.org

Methods & accuracy

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