Estimates of the Earth's average albedo vary in the range 0.3–0.4, resulting in different estimated effective temperatures. Estimates are often based on the solar constant (total insolation power density) rather than the temperature, size, and distance of the Sun. For example, using 0.4 for albedo, and an insolation of 1400 W m, one obtains an effective temperature of about 245 K. Similarly using albedo 0.3 and solar constant of 1372 W m, one obtains an effective temperature of 255 K.