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The Stefan–Boltzmann law gives the radiated luminosityFor radiative mass loss at fixed luminosity, using mass-energy equivalence, the mass-loss magnitude and one-percent time areThe numerical constants are the external CODATA 2014 $\sigma =5.670367\times 10^{-8}\mathrm{W}{\mathrm{m}}^{-2}{\mathrm{K}}^{-4}$ and $c=299792458\mathrm{m}{\mathrm{s}}^{-1}$; years here mean 365.25 days.^[ref] This estimates radiative mass loss with the supplied radius and temperature held constant. It does not predict a real stellar lifetime or include solar-wind mass loss.

For luminosity $L$, mass-energy equivalence gives $|\dot{M}|=L/c^2$. Holding $L$ constant gives a time $t=fM{c}^2/L$ to radiate a mass fraction $f$. A blackbody estimate uses the Stefan–Boltzmann law, $L=4\pi R^2\sigma T^4$. This is a radiative-energy estimate, not a model of a star's evolving nuclear fuel or mass loss in a wind.