HI mschlie, Your employer uses your submitted Form W-4 and the IRS withholding tables to calculate your federal tax withholding.
There is a W-4 Calculator that will take you step-by-step through the Form W-4,
https://turbotax.intuit.com/tax-tools/calculators/w4/
Once you complete the form, give it to your employer. Then, keep a close eye on your next few paychecks to see how the changes impacted your federal income tax withholding.
I hope this is helpful!
https://turbotax.intuit.com/tax-tools/calculators/w4/
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