Measure the distance travelled by the substance from the starting line
Measure the distance travelled by the solvent front from the starting line
Divide the substance distance by the solvent front distance
Use the formula: RF value = distance travelled by substance / distance travelled by solvent front
Ensure both distances are measured from the same starting point
Keep units the same for both measurements
Record the RF value as a decimal or fraction
Repeat the calculation for each spot if there is more than one