HouseMath support

Mortgage, affordability and buy-versus-rent calculator for iPhone

Frequently asked

Why doesn't the property tax match what I was quoted?

The rate shown is a statewide approximation of what a buyer typically pays on a newly purchased home. Real rates vary considerably by county, city and school district. Tap the tax rate field and type your own. The app will use yours and mark it as custom.

Why is the tax rate higher than the "effective rate" I read elsewhere?

Published effective rates divide total tax paid by market value across all homeowners. In states that cap assessment growth, such as California under Proposition 13, Florida under Save Our Homes, Oregon and Michigan, long-held homes are assessed far below market value. That pulls the average well below what someone buying today is actually billed. HouseMath shows the new-purchase figure because that is what applies when you buy.

Where does the interest rate come from?

The Freddie Mac Primary Mortgage Market Survey, published weekly and retrieved from the Federal Reserve Bank of St. Louis. The app fetches both the 30 year and the 15 year rate and picks the one matching your loan term, interpolating in between. The survey date is shown in the app. Recent values are built in so it works offline; tap Refresh rates to fetch the latest. These are national averages rather than a quote for you, so your lender's rate will depend on your credit, down payment and loan type.

How is PMI calculated?

When your down payment is under 20%, mortgage insurance is added automatically at a rate based on your loan-to-value ratio. The schedule stops charging it once the balance reaches 78% of the home's value, which is the automatic termination point under the federal Homeowners Protection Act. You can change the rate or switch it off entirely.

Can I enter insurance as a monthly amount?

Yes. The insurance section accepts a monthly amount, an annual premium, or a percentage of the purchase price. Switch between them and the dollar figure is preserved.

Which version am I running?

Tap the ⓘ button at the top left of any tab. The version and build sit at the top of that menu, written like 1.0 (1), above the links to report a bug and to this page. Quote that number if you write to us, because the answer often depends on it.

Does the app track me or collect my data?

No. There are no accounts, analytics, advertising or tracking. Everything you enter is stored only on your device. See the privacy policy.

Important

HouseMath is an estimating tool. Tax and insurance figures are approximations held flat over the life of the loan, and the app does not provide financial, tax or legal advice or any offer of credit. Confirm real costs with your lender, insurer and local tax authority.

© 2026 Gray Glen LLC