# Understanding federal tax withholding on my pay stub?

Because I am a masochist and want my pay stubs in a spreadsheet format on my computer I am looking into the formulas used to calculate federal income tax. I read over IRS Publication 15 Circular E and got the following:

Single Semi-monthly 2 Exemptions = 2 * 154.17 = 308.34 Gross pay: 1,870

Using 25% of income over 1525 + 197.85 I get 1870 - 308.34 = 1561.66 - 1525 = 36.66 * 25% = 9.165 + 197.85 = 207.015

However, paycheckcity.com and my pay stub both agree that 207.08 is being withheld. Where am I missing 6 cents from?

Using another week where I was on unpaid leave, gross pay of 850 I calculated 50.35 would be withheld, when in actuality 50.42 was withheld, so I was 7 cents off that pay period. Just seems odd that I am getting so close but not exact.

• At least you recognize that you are in fact a masochist for computing to this level of detail :) Jun 23 '11 at 21:36
• I have mild OCD when it comes to problem solving. I am a computer programmer (recent graduate) and I hate knowing that there is a problem I am close to solving but not quite there. It's like a little fly in the corner of my vision, not doing any harm, but still annoying. Jun 23 '11 at 21:54