If your only income is social security, it is tax-free.
If half your social security plus all your other taxable income is less than $32,000, your social security is still tax-free, and your other income would be subject to the standard deduction of $30,700, so it would probably still be tax-free.
If half your social security plus all your other taxable income is more than $32,000, then your other taxable income is taxable, AND you start to count your SS benefit as taxable income, but you are still subject to the $30,700 standard deduction.
So even if you planned to have $50,000 of other income (pensions, 401k etc.) your first $30K would be tax-free and the next 30K would be 12%, which averages to 6%.
I suspect that 10%-12% would be sufficient. If you want to be conservative, start with 15% and do a checkup halfway through the year.
This all assumes you are married and filing jointly. If you file separately, that changes everything.
