There are at least several formulas to calculate, or I should better say approximate, the circumference of an ellipse. Although calculating the circumference of a circle is very easy, calculating the circumference of an ellipse is a very difficult task.

**C ≈ Π × [3 × (R + r) - √ (R + 3 × r)(3 × R + r)]**

Where *C* is circumference, *π* is 3.14, *R* is the semi-major axis, and *r* is semi-minor axis.

The Ramanujan formula that is presented above keeps things simple providing a fair accurate result. For the sake of simplicity I have decided it is the best formula to be known. Other formulas, more accurate, use infinite calculations, factorials, and many other strange Math things.

Example:

If R = 4 and r = 2 then C = ?

C ≈ Π × [3 × (R + r) - √ (R + 3 × r)(3 × R + r)] ≈

≈ 3.14 × [3 × (4 + 2) - √ (4 + 3 × 2)(3 × 4 + 2)] ≈

≈ 3.14 × (18 - √ 140) ≈

≈ 3.14 × (18 - 11.83) ≈

≈ 3.14 × 6.17 ≈ 19.37