Should You Overpay Your Mortgage to Kill PMI Faster, or Invest That Money Instead?

Two ways to spend the same $300/month

We ran a common scenario: a $350,000 home, $315,000 balance (90% LTV), $200/month PMI premium. Paying an extra $300/month toward principal reaches the 80% LTV removal threshold about 10 months sooner than the standard payment schedule alone — freeing up that PMI premium 10 months early. Whether that beats investing the same $300/month instead depends entirely on the gap between your mortgage rate and your realistic investment return assumption.

How the math works

The tool simulates your loan balance forward month by month on the standard payment schedule until it reaches 80% of home value (the borrower-requested PMI removal threshold under the federal Homeowners Protection Act), then repeats the simulation with your extra payment added. The gap between the two is the months saved, worth the PMI premium for each month avoided.

To compare fairly against investing instead, extra principal payments are treated as earning a guaranteed "return" equal to your mortgage rate — the interest they avoid — the standard framing for any pay-down-debt-vs-invest decision. That, plus the PMI saved, is compared against the same recurring amount growing at your assumed investment return with PMI paid in full the whole time.

What this tool doesn't model: home value appreciation (which reaches 80% LTV faster than payments alone — a rising market can remove PMI without any extra payments at all), your loan's specific automatic-termination LTV (78% by federal law, separate from the 80% borrower-requested threshold this tool models), or the paperwork/appraisal requirements some servicers impose for early PMI removal requests.

Math runs locally. Inputs never leave your browser.Source on github.

Where this framework misses something real

• Home values rarely stay flat.If your area has been appreciating, you may already be at or near 80% LTV based on current value, even without any extra payments — get a current valuation before assuming you need to overpay at all. A cheap appraisal or broker price opinion can settle this faster than months of extra payments.
• Your investment return assumption needs to be realistic, not aspirational.The "invest instead" case only wins with a return assumption meaningfully above your mortgage rate, sustained reliably — a single good year doesn't validate the comparison over a multi-year horizon.
• Extra payments reduce flexibility.Money paid into home equity is illiquid — you can't easily access it in an emergency the way you could a taxable investment account. If your emergency fund isn't solid, that liquidity has value this pure math doesn't price in.
• Some loans have PMI terms beyond simple LTV.A few loan types (certain high-LTV or high-risk originations) require PMI for a minimum period regardless of LTV — confirm your specific loan's terms with your servicer before planning around the 80% threshold.

What to actually do with this number

1. Check your home's current value first — appreciation alone may have already gotten you close to 80% LTV.
2. If not, decide on a realistic extra-payment amount and a realistic investment-return assumption, not an aspirational one.
3. Make sure your emergency fund is solid before committing extra cash to illiquid home equity.
4. Once you hit 80% LTV, contact your servicer proactively — PMI removal is often borrower-initiated, not automatic, until the later 78% threshold.
5. Confirm your specific loan's PMI removal terms and any appraisal requirements with your servicer.