You can use the TaxCaster to estimate the effects of the withdrawal.
https://turbotax.intuit.com/tax-tools/calculators/taxcaster/
If your only other income is SSI, it is tax-free. Once you start to have other taxable income, not only is that income taxable, but there is also the possibility that part of your SSI will also be taxed. Since it's a complicated formula and something of a moving target, some kind of software tool is going to give you the best estimate.
If you are under age 59-1/2 and NOT permanently and totally disabled, then there will be an extra 10% penalty on the IRA withdrawal, on top of the regular income tax. If you are over 59-1/2, or you are under that age but disabled, there is no additional penalty.
