Free · 2D geometry calculators 📏

Ellipse Area from Two Semi-Axes

Calculate ellipse area from two semi-axes with converted units, positive geometric inverses and explicit model limits.

Calculator inputs

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Enter the known values in the units shown. Results update as you type.
Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
Use the worked example to check the method. Reset restores the starting fields.

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An ellipse with semi-axes 2 cm and 3 cm encloses area 6π cm². Its complete axis lengths are 4 cm and 6 cm.

A = πab; full axes = 2a and 2b

Enter these known values and leave the other values blank.

Enter the two distances from the center to the ellipse boundary along perpendicular axes. These are semi-axes, not the full width and height; either axis may be larger.
Measurements must describe the same shape. Clear a quantity you want to infer instead of supplying conflicting measurements. Unit selectors are converted before the geometric relationships are applied.
Calculations use 64 significant digits with full-precision π; result formatting rounds the displayed value separately. These are ideal geometric models, without material allowances or measurement uncertainty.

Divide each full axis length by two before entering it. Equivalently, area is π times full width times full height divided by four.

The international acre is exactly 43560 square international feet; Bookify replaces the rounded captured area factor.