Planet Equilibrium Temperature Calculator

Find a planet's blackbody equilibrium temperature in kelvin and Celsius from orbital distance, bond albedo, and stellar luminosity. Free, instant.

Frequently Asked Questions

What is equilibrium temperature?

It is the temperature a planet would reach as a simple blackbody, balancing absorbed starlight against radiated heat, before any atmosphere is considered.

Why is the real temperature often higher?

A greenhouse atmosphere traps heat and can lift the surface temperature well above the equilibrium value, as on Venus.

What is bond albedo?

Bond albedo is the fraction of all incoming starlight that a planet reflects back into space across every wavelength.

What is the equilibrium temperature of Earth, Venus, and Mars?

Using each planet's bond albedo and orbital distance, this model gives about 255 K (−18 °C) for Earth, roughly 227 K (−46 °C) for Venus, and about 210 K (−63 °C) for Mars. These are baseline blackbody values before any atmosphere; real surfaces can differ sharply. Venus is the extreme case, where a thick carbon-dioxide atmosphere lifts the actual surface to around 460 °C through the greenhouse effect.

Important Disclaimer: Estimates for informational purposes only.

This calculator provides estimates for informational purposes only. Results are based on assumptions and may not reflect actual outcomes. Consult qualified professionals in relevant fields before making important decisions based on these results.