We first give formulas for several distance measures, and then describe them in more detail further down. Defining the "Hubble distance" as d H = c H 0 ≈ ≈ 3000 h − − 1 Mpc ≈ ≈ 9.26 ⋅ ⋅ 10 25 h − − 1 m where c is the speed of light, H 0 is the Hubble parameter today, and h is the dimensionless Hubble constant, all the distances are asymptotic to z ⋅ ⋅ d H for small z.