If you itemize, mortgage interest is deductible. See roughly what it saves.
A mortgage interest tax savings calculator estimates how much you save on income tax by deducting mortgage interest, if you itemize deductions rather than taking the standard deduction.
Mortgage interest on a primary (and sometimes second) home is deductible if you itemize. The savings equal the interest times your marginal tax rate, so a higher bracket means a bigger benefit. Interest is highest in the early years of a loan, so the deduction is largest then and shrinks over time.
The deduction only helps if your total itemized deductions exceed the standard deduction, which is large for most filers. Many homeowners find the standard deduction is bigger, so they get no extra benefit from mortgage interest. Add up all your itemized deductions before assuming the mortgage saves you tax.
Yes, if you itemize deductions, on up to a limit of mortgage debt. If you take the standard deduction, there's no additional benefit.
Roughly the interest paid times your marginal tax rate, but only for the amount your itemized deductions exceed the standard deduction.
Rarely. You spend a dollar of interest to save only your tax rate on it, so it's not a reason on its own to carry debt.
See the exact formula and a worked example on our methodology page.