If I went back back to 12% 401k would that bring me back down to ~6%?
Federal Income Tax = Single w/ 2 claimed allowances.
Assuming 26 * "gross paycheck" is the annual income, filing single with 2 exemptions (see the case study spreadsheet) gives the following for (annual federal tax)/26:
Previous
no 401k $63.65
6% 401k $47.16
12% 401k $36.16
After Raise
no 401k $109.36
6% 401k $96.72
12% 401k $84.08
Thanks a ton, friend. The calculations you have are still off from my paycheck though (looks like I am paying more), what could be the reasoning for this?
Something that nobody's pointed out explicitly yet, that you may or may not be aware of: your withholding does not equal your end of year tax burden, necessarily or even commonly. Your total tax rate after exemptions does not equal your marginal tax rate, and the withholding change is calculated essentially at your marginal tax rate. Additionally, the tables make no allowance for a mid-year increase; i.e., they calculate as if you'd been receiving the higher rate for the full year.
Your deductions and exemptions haven't changed, only your gross income, so the increase will be taxed at your top rate, probably 15% judging from your hourly rate. This can make your withholding increase look like a lot if your exemptions/deductions previously had you near an effective tax rate of zero. This is especially true if you previously would have gotten the earned income credit, that sort of thing.
If your tax situation is fairly simple, the withholding is likely to be close going forward; if you received a raise mid-year, you'll get some money back when you file at least this first year. You can use tools like Taxcaster to forecast it, and adjust as necessary.
https://turbotax.intuit.com/tax-tools/calculators/taxcaster/