For the calculation of dilution factor, you can divide the final volume by the initial volume.

DF= Vf/Vi

Where, DF is dilution factor

              Vf is final volume

               Vi is initial volume.

For example, if you dilute 1 mL of aliquot  into 9 mL of diluent, you can calculate using the above equation as,

DF= (1+9)mL/1mL

     = 10

The dilution factor is 10.

Simply a ratio of final volume of solution to the initial volume. Main concern while calculation is unit of measurement should be same.

Hi Farideh Amini-Birami . The dilution factor = volume taken / total volume .