Kepler-186f is thought to be 97% and 125% the size of Earth (1.11 ± 0.14 the size of Earth) While its mass is not know it is thought to be up to 1.4 times Earth's. The true mass depends on what the planet is made of. If the planet has no atmosphere, then its temprature would be around 182 Kelvin (-91 Celsius). 