Geometry
Area of an ellipse
The circle area formula with the two radii allowed to differ.
The Formula
A = pi x a x b
The circle area formula with the two radii allowed to differ.
| Symbol | Meaning | Unit | Notes |
|---|---|---|---|
| A | Area | square units | Enclosed area of the ellipse. |
| a | Semi-major axis | units | Half the longest distance across. |
| b | Semi-minor axis | units | Half the shortest distance across. |
| pi | Pi | none | The circle constant, about 3.14159. |
What Each Symbol Means
Asquare units
Area
Enclosed area of the ellipse.
aunits
Semi-major axis
Half the longest distance across.
bunits
Semi-minor axis
Half the shortest distance across.
pinone
Pi
The circle constant, about 3.14159.
See It Worked With Real Numbers
A formula on its own does not tell you which number goes where. The how to calculate the area of an ellipse page applies this equation to a concrete case, shows every intermediate step, and names the mistakes that produce a wrong answer even when the algebra is right.
Where This Formula Appears
This equation is the working core of How To Calculate The Area Of An Ellipse, filed under Math. Every number the guide produces comes from substituting into this one line.