The first thing that you have to determine is whether you can make a deductible contribution to a Traditional IRA. A contribution to a ROTH IRA or a non-deductible contribution to a Traditional IRA is not deductible and makes no difference to your tax.
You can determine whether you can make a deductible contribution to a Traditional IRA by reviewing the requirements in IRS Pub. 590a, at this link:
http://www.irs.gov/pub/irs-pdf/p590a.pdfNow, if you have determined that you can make a deductible contribution to a Traditional IRA, then the amount that you have to contribute to reduce your tax to zero depends on what your marginal tax rate is. If your marginal tax rate is 20% and you want to offset $200 in tax, then you have to contribute 200/0.2 = $1,000.