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Results
Enter your dimensions above and the results appear here.
About the Ellipse Calculator
The ellipse calculator is a free online tool: area, perimeter, eccentricity and foci. Enter semi-axis a and semi-axis b and the results update instantly, alongside a labelled diagram so you always know which measurement goes where.
Choose your input unit (mm, cm, m, km, in, ft or yd) and optionally show the results in a different one: lengths, areas and volumes are converted correctly. Every answer shows the formula behind it, and the calculation runs in your browser, so nothing is uploaded.
Ellipse Calculator example
Semi-axis a = 7 cm
Semi-axis b = 4 cmArea = 87.9646 cm²
Perimeter (approx.) = 35.2031 cm
Eccentricity = 0.8207
Focal distance c = 5.7446 cm
Distance between foci = 11.4891 cmHow to use the Ellipse Calculator
- Pick the unit your measurements use. All dimensions must share the same unit.
- Enter semi-axis a and semi-axis b. Focus a field to highlight the matching label on the diagram.
- Read the results as you type. The largest card is the main answer; the others are the related measurements.
- Copy a single value, copy everything, or share a link that keeps your inputs.
Ellipse Calculator FAQ
What formulas does the ellipse calculator use?
A = πab; P ≈ π[3(a+b) − √((3a+b)(a+3b))]; c = √(a² − b²); e = c / a.
Can I use different units?
Yes. Pick the input unit and, if you like, a different output unit. Area results are shown in squared units and volumes in cubed units.
Is this ellipse calculator free and private?
Yes. It is free with no sign-up, and calculations happen on your device, so your numbers are never sent to a server.
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