Stellar Luminosity Calculator

It applies the Stefan-Boltzmann law, so luminosity scales with radius squared times temperature to the fourth power, capturing both how big and how hot a star is.

Because temperature enters to the fourth power, a modest rise in surface temperature raises output steeply, so a hot star can far outshine a cooler star of the same size.

It gives the total energy output in watts and as a multiple of the Sun luminosity, so you can compare a star directly to our own.

A star luminosity is the total power it radiates in every direction, and the Stefan-Boltzmann law ties it neatly to just two things: how big the star is and how hot its surface is. Luminosity equals four pi times the radius squared, times the Stefan-Boltzmann constant, times the temperature to the fourth power.

Yes. Stellar Luminosity Calculator is completely free, with no sign-up and no usage limits.

Yes. Stellar Luminosity Calculator runs in any modern web browser. There is nothing to download or install.

Yes. Stellar Luminosity Calculator runs entirely on your device in your browser, so nothing you enter is uploaded to a server.