Currently, my federal income tax is a calculation of my adjusted gross income and tax rate, and I think there is an error or something I am missing.
Taxable income. Your Exemption and Deductions (Standard or Itemized) are subtracted from your adjusted gross income to arrive at taxable income.
Please see TurboTaxMark's answer on figuring your tax rate https://ttlc.intuit.com/replies/6251963