Mortgage interest is only fully deductible on debt up to $750,000 for loans originated after December 15, 2017 — interest on any balance above that is prorated down.
How it works
The deduction limit divided by the loan balance (capped at 100%) gives the deductible percentage. Multiplying that percentage by the interest actually paid gives the deductible interest amount.
What this does not include
Loans originated on or before December 15, 2017 are generally grandfathered under the prior $1,000,000 limit — this calculator uses the newer $750,000 cap for post-2017 loans, not the grandfathered figure.
How to use this calculator
- Enter your average mortgage balance for the year and total interest paid.
Frequently asked questions
Does this limit apply to home equity debt too?
The $750,000 limit is a combined cap on acquisition debt (used to buy, build, or substantially improve the home) — home equity debt used for other purposes generally isn’t deductible at all under current law.
Is this limit per person or per household?
It’s $750,000 total for a married couple filing jointly, or $375,000 each if married filing separately — not $750,000 per spouse.
Does refinancing reset the grandfathered $1,000,000 limit?
Generally no, as long as the refinanced loan doesn’t exceed the original acquisition debt balance — refinancing to a larger balance can lose grandfathered status on the excess.
