Ellipse Calculator

Calculate ellipse area and approximate circumference.

Semi-major Axis (a)Semi-minor Axis (b)

Enter axis lengths above.

How to Use the Ellipse Calculator

Enter the semi-major and semi-minor axes to calculate ellipse area and an approximate circumference.

Practical Example

With semi-axes 6 and 4, the area is approximately 75.40 square units.

Factors That Affect the Result

Area is exact from the two semi-axes, while circumference typically uses an approximation. Confirm whether your measurements are radii or full axis lengths.

Frequently Asked Questions

What is a semi-major axis?

It is half the longest diameter of the ellipse.

Is circumference exact?

Most simple calculators use a close approximation.

Can I enter full diameters?

Divide them by two first if the tool expects semi-axes.

Related Tools

Interpreting Ellipse Measurements

An ellipse uses two semi-axes rather than one radius. Area is πab, where a and b are the semi-major and semi-minor axes. If full width and height are measured, divide each by two before applying the formula.

Ellipse circumference does not have the same simple exact expression as a circle, so calculators commonly use a close approximation. For engineering or fabrication work that requires very high precision, confirm which approximation is being used. Keep both axes in the same unit and avoid confusing diameter-like full dimensions with semi-axis values.