Question: how to calculate the gross from net?
Answer: Total the tax percentages. Social Security 6.2% + Medicare 1.45% = 7.65%
Subtract the total from 100% 100-7.65 = 92.35.
Convert that number to a percentage by moving the decimal two positions to the left. ... 
Add $100 from FIT to the net. ... 
Divide the new net amount by the amount in step. ... 
The gross amount to be used is $324.85.