The basic dimensions in physics are length, mass and time, which are commonly expressed in the SI system of units as the metre, the kilogram and the second. In particle physics, the typical scale of quantities is lengths of 10^ {-15}mathrm {m} 10−15m, masses of 10^ {-27}mathrm {kg} 10−27kg and durations of 10^ {-7}mathrm {s} 10−7s

For in natural (Planck) units, the strength of gravity simply is what it is, a primary quantity, while the proton's mass is the tiny number 1/13 quintillion.