First of all you need to see if have enough total itemized deductions to itemize since the Standard Deduction is now more. Then only the amount that puts you over the standard deduction helps. But it's not a 1:1 reduction. It only reduces your tax by your tax rate. So if you are in the 25% tax bracket a $100 deduction will reduce the tax by $25.
For 2020 the standard deduction amounts are:
Single 12,400 + 1,650 for 65 and over or blind (14,050)
HOH 18,650 + 1,650 for 65 and over or blind
Joint 24,800 + 1,300 for each 65 and over or blind
Married filing Separate 12,400 + 1,300 for 65 and over or blind
