Ellipse Calculator

An ellipse is a graceful oval shape defined by two axes: the semi-major (a) and semi-minor (b). Our Ellipse Calculator delivers instant, accurate values for area, perimeter (circumference), eccentricity, and focal distance. The area is simply π × a × b. For perimeter, we use the famous Ramanujan approximation: P ≈ π [3(a+b) – √((3a+b)(a+3b))], which is remarkably accurate for most ellipses. Eccentricity e = √(1 – b²/a²) tells you how “stretched” the ellipse is (0 = circle, approaching 1 = flat). The focal distance from the center is c = √(a² – b²).

Whether you’re an architecture student, a graphic designer, or an engineer working on reflective properties (whispering galleries, ellipses have fascinating focal points), this tool saves time and prevents errors. Just input a and b (positive numbers, with a ≥ b) and get comprehensive results. The calculator automatically handles decimal values, large numbers, and swaps if b accidentally exceeds a (it will normalize by treating the larger as semi-major). This ensures you always see meaningful numbers. The Reset button brings back the default example (a=8, b=5) so you can experiment.

We developed this Ellipse Calculator for MultiCalculators.org, a growing collection of free, no‑nonsense utilities. The design is fully responsive – it works on phones, tablets, and desktops. The interface is clean, with high‑contrast text and ample touch targets. Use it for homework, quick prototyping, or curiosity. Every result updates in real‑time (well, after clicking Calculate). And because we believe in open, useful tools, there’s no registration, no paywall, and no clutter. If you need more advanced ellipse features (arc length, latus rectum), let us know through our Contact page. We hope this helps you work faster and smarter!