What is orbital eccentricity?

A measure of how much an orbit deviates from circular, from 0 (circle) to nearly 1 (elongated ellipse).

How is eccentricity calculated?

(apoapsis − periapsis) ÷ (apoapsis + periapsis).

Why does eccentricity matter for climate or comets?

It causes large variations in distance from the central body, affecting temperature and speed.

Orbital Eccentricity Calculator - CalculatorLabs.net

Orbital Eccentricity Calculator

Orbital eccentricity describes how far an orbit deviates from a perfect circle — a value of 0 is a perfect circle, while values approaching 1 describe increasingly elongated ellipses.

Apoapsis Distance (farthest)

Periapsis Distance (closest)

Instant Result

Eccentricity -

What Is a Orbital Eccentricity Calculator?

Orbital eccentricity describes how far an orbit deviates from a perfect circle — a value of 0 is a perfect circle, while values approaching 1 describe increasingly elongated ellipses. This calculator finds eccentricity from the closest (periapsis) and farthest (apoapsis) points of an orbit.

How to Use This Orbital Eccentricity Calculator

Enter the apoapsis distance — the farthest point in the orbit from the central body.
Enter the periapsis distance — the closest point in the orbit.
Click Calculate to get the orbital eccentricity.

Formula

Eccentricity = (apoapsis − periapsis) / (apoapsis + periapsis)

Worked Example

Earth's orbit ranges from about 147.1 million km (periapsis) to 152.1 million km (apoapsis). Eccentricity = (152.1−147.1)/(152.1+147.1) ≈ 0.0167 — very close to a perfect circle.