Your refund is dependent on many factors; you have listed only 2 of them. After reviewing your W-2 entries, print out your tax return and look at line 16 which is the total tax you owe. Compare that to what is in Box 2 of your W-2 which is the income taxes you paid.
If you are not receiving the refund you expected, you may want to give your employer an updated W-4 form. The W-4 is what determines the amounts withheld from your paycheck which directly affects your refund amount. See this article for more information - Form W-4 and Your Take-Home Pay.