How much taxes should i withold from social security

Withholding from social security replaces or reduces estimated tax payments.

so you have to estimate your total tax liability.

@perrya2 

It depends on your other income. If Social Security is your only income, you do not have to pay any tax or even file a tax return. If you have other income, the tax on your Social Security will depend on the amount of other income. Any tax that you have withheld from Social Security will be applied to your total tax, on all your income.

You can use TaxCaster to estimate your total federal tax.