Its usually because of Excel showing only two decimal places instead of the
complete value in a cell. The result of a formula may be for example
453.558944512 but the cell will display 453.56. In calculations though the
full number will be used giving unexpected differences. You can get round
this (no pun intended) by using the ROUND function, try
=ROUND((your_formula),2) eg =ROUND((VLOOKUP,A1,B1:B500,2,FALSE),2)
This will eliminate decimal places over two the calculations shoul then be
correct,
Regards,
Alan.