Luminosity Calculator

Calculate stellar luminosity using Stefan-Boltzmann law
Radius relative to the Sun (Sun = 1.0)
Effective surface temperature in Kelvin
Stellar Luminosity
Solar Luminosities (L☉)
Watts
Star Classification
Color:
Brightness:
Comparison with the Sun
Radius Ratio
Temperature Ratio
Luminosity Ratio
Stefan-Boltzmann Law
Formula:
L = 4πR²σT⁴

Where:

  • L = Luminosity (energy radiated per second)
  • R = Radius of the star
  • σ = 5.67×10⁻⁸ W/(m²·K⁴) (Stefan-Boltzmann constant)
  • T = Surface temperature in Kelvin
Simplified Formula (Solar Units):
L/L☉ = (R/R☉)² × (T/T☉)⁴

This calculator uses the Stefan-Boltzmann law to determine how much energy a star radiates based on its size and temperature. Luminosity increases dramatically with both radius and temperature.

Features

  • Calculate stellar luminosity using the Stefan-Boltzmann law
  • Results in solar luminosities and watts
  • Automatic spectral classification based on temperature
  • Preset values for famous stars
  • Visual comparison with the Sun
  • Color and type classification for stars

How to Use

  1. Enter the star's radius in solar radii (Sun = 1.0)
  2. Enter the star's surface temperature in Kelvin
  3. Or select a preset star from the dropdown
  4. View the calculated luminosity and spectral classification