@gagan5987 - if you are using Turbo Tax, then you have access the worksheet in question. Instructions were provided earlier in this thread. In fact, trust the software is calculating everything ocrrectly. don't over think it.
If you are not using Turbo Tax (and trying to do this with pencil and paper), high risk of getting it incorrect as you need to complete the worksheet to determine the tax. the worksheet is on page D-16 at this link https://www.irs.gov/pub/irs-pdf/i1040sd.pdf
