Hubble constant is most frequently quoted in (km/s)/Mpc, thus giving the speed in km/s of a galaxy away, and its value is about . However, the SI unit of "H"0 is simply s−1, and the SI unit for the reciprocal of "H"0 is simply the second. The reciprocal of "H"0 is known as the Hubble time. The Hubble constant can also be interpreted as the relative rate of expansion. In this form H0 = 7%/Gyr, meaning that at the current rate of expansion it takes a billion years for an unbound structure to grow by 7%.