Hi there,
Your social security income may or may not be subject to income tax, depending on your total income.
If your Social Security Income is taxable then it is taxed at the standard tax rate based on your total income. Whether or not it is taxable and how much of it is taxable is based on your income outside of Social Security, as well as your filing status.
You may find this link informative: https://www.ssa.gov/benefits/retirement/planner/taxes.html