Mass of photon

A  mass of a photon can be calculated by Einstein's equation

E = mc²

m = e/c² 

and 

Energy of a photon = h(Planks Constant) * c(speed of light ) / wavelength

.

so mass of a photon = (hc/wavelength )/c²

m = 6.626*10^-34/wavelength / 299792458

for a light ray of red colour

wavelength = approx 400nm = 4 * 10^-7m

so 

m =( 6.626*10-34 / 4 * 10^-7 )/ 299792458 

= 5.525489236957388701219428275277 * 10-36 kg

for a photon of red colour with wavelength = 400nm

this way we can calculate the mass of any photon with a known value of wavelength or frequency