Exoplanet Discovery Calculator

Written by Great Medico

Updated September 25, 2026 •2 min read

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When you need a quick exoplanet discovery check, the useful number is the one you can reproduce. Astrophysics formulas often look compact while hiding assumptions about circular orbits, ideal radiation, or simplified cosmology. The goal is to make the equation, inputs, and result easy to sanity-check rather than hide them behind a black box.

What this calculator does

This calculator focuses on planet radius from Observed transit depth, Host star radius, Planet radius. It is designed for quick estimation and hand-checking, with the visible fields defining the scope of the model rather than implying a larger simulation.

How to use it

Start with Observed transit depth, Host star radius, Planet radius, Planet orbital period, Host star mass. Let the unit controls handle supported conversions instead of converting values mentally. Set Exoplanet value to calculate to match the solve path you want. If the page offers both inputs and derived fields, fill the quantities you know and leave result fields for the calculator.

How the calculation works

Transit depth follows δ = (Rp/Rs)², while planet radius is Rp = Rs√δ. The semi-major-axis mode uses Kepler’s relation a = [GMP²/(4π²)]^(1/3). Each mode uses a different subset of the visible fields.

Example

With the default setup (Exoplanet value to calculate = Planet radius; Observed transit depth = 1 %; Host star radius = 1 R☉; Planet radius = 1 R♃), the page reports planet radius of 10.919793 R⊕. Reproducing this default result is a quick way to verify units before replacing the values with your own case.

How to interpret the result

The planet radius is a model-dependent astrophysical quantity. Keep track of whether distances are radii, altitudes, parsecs, light-years, or orbital semi-major axes, and do not interpret supporting approximations as direct observations.

Limitations and notes

The transit model assumes a simple area ratio and ignores limb darkening, grazing geometry, dilution, eccentric transit effects, and measurement uncertainty. In the current transit-depth solve path, the Planet radius field is labeled with R♃ by default but is numerically converted with an Earth-radius constant, so do not use that mode for precision work until the unit handling is corrected.