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GeomBench
π × a × b — a circle's formula generalised to two radii.
When a = b, the ellipse area formula π·a·b collapses to π·r² — the familiar circle area formula. An ellipse is simply a circle stretched along one axis.
Unlike area, an ellipse's circumference has no simple closed-form formula. We use Ramanujan's well-known approximation, which is accurate to within a tiny fraction of a percent for most real ellipses.
Area
75.398
What you entered
Area = π × a × b
π × 6 × 4= 75.3982Circumference (Ramanujan's approximation)
π × [3(a+b) − √((3a+b)(a+3b))]= 31.7309Result
Area: 75.398
An ellipse with semi-axes 6 and 4 has an area of 75.398 and an estimated circumference of 31.731.