Mortgage Interest Deduction Calculator
What the deduction is genuinely worth to you, federal and state — starting with whether itemizing beats the standard deduction at all.
State and local taxes (capped at $10,000), charitable giving, medical. This decides whether itemizing wins.
Federal at 22% plus California at 13.3%, applied to the amount by which itemizing beats the standard deduction.
Only $2,750 of your $22,750 in interest is doing any work. The rest is absorbed closing the gap to the standard deduction you would have received regardless.
The question almost every calculator skips
Most mortgage interest calculators multiply your interest by your tax rate and present the result as your saving. That is wrong for the majority of households, and the reason is the standard deduction.
You only benefit from itemizing to the extent your itemized total exceeds the standard deduction. Pay $14,000 in mortgage interest, add $10,000 of state and local taxes, and if the standard deduction for your filing status is close to that combined figure, the deduction is worth little or nothing. The first dollars of interest buy you no tax benefit at all — they only close the gap to a number you’d have received anyway.
Since the standard deduction roughly doubled in 2018, most filers take it. If you’re in that group, the honest answer is that your mortgage interest has no tax value, and any calculator telling you otherwise is flattering you.
The limits that apply if you do itemize
Interest is deductible on up to $750,000 of acquisition debt for loans taken out after 15 December 2017, or $375,000 if you file separately. Older loans generally keep the previous $1 million limit. Acquisition debt means the money went into buying, building or substantially improving the home that secures the loan — which is also the test that decides whether home equity borrowing qualifies.
Then your state does something different
The federal calculation is only half of it. Some states conform to federal itemized deductions, some set their own limits, and nine have no income tax at all — in which case the federal deduction is the whole story. The difference between a high-rate conforming state and a no-tax state can be thousands of dollars a year on identical loans.
Our state-by-state guide covers the rules and rates where you live, and there’s a page for each state with its own numbers.
Where to look it up
Your Form 1098 from the servicer reports the mortgage interest you paid, and the property tax actually disbursed if you escrow. The authority for all of this is IRS Publication 936, which sets out the debt limits, the acquisition-debt test and the treatment of points. Tax year shown here is 2025.