What is the formula for calculating the temperature of a star?

Well, sweetheart, to calculate the temperature of a star, you can use Wien's Law which states that the temperature is inversely proportional to the peak wavelength of its emitted radiation. Another way is to use the Stefan-Boltzmann Law, which relates a star's luminosity and surface area to its temperature. So just plug those numbers in and bam, you've got yourself a hot, steamy star temperature!