Please tell us how do you calculate the Social Security Benefits taxable amount?

[VolvoGirl]

You don't.  You enter the SSA-1099 into Turbo Tax and it automatically calculates the taxable amount depending on your other income.

Try going to the search box by My Account and type in Social Security Benefits.  That will give you a Jump To link to take you directly to it.

OR Enter a SSA-1099, SSA-1099-SM or RRB-1099  under
Federal Taxes tab
Wages and Income tab
Then scroll down to Retirement Plans and Social Security
Social Security (SSA-1099. RRB-1099) - click the Start or Update button

[VolvoGirl]

Up to 85% of Social Security becomes taxable when all your other income plus 1/2 your social security, reaches:
Married Filing Jointly: $32,000
Single or head of household: $25,000
Married Filing Separately: 0

To see the Social Security Benefits Calculation Worksheet  in Turbo Tax Online version you would have to save your return with all the worksheets to your computer.   Or if you are using the Desktop CD/Download Software you can switch to Forms Mode (click Forms in the upper right) and click on SS in the list on the right side.

[jerry2000]

The amount of your SS benefit that is taxable is calculated in accordance with the details in IRS Pub. 915, which you can find here:
https://www.irs.gov/pub/irs-pdf/p915.pdf

If you are using the worksheet on the back of your SSA-1099 and getting a different result than Turbotax gets, then you have a mistake in your calculations. For whatever reason, most people who use that worksheet get the wrong answer.