About Math for Landlords

Free calculators and guides for small landlords in the United States: people who own one to a few rental homes and want to check a deal, price a partial month or understand their taxes.

Who builds this site

Math for Landlords is an independent project run by a developer with a background in networks and systems. It is not a law firm, a lender or a tax firm, and nobody here is an attorney, CPA or licensed real estate professional. That is why the rules on the site are taken from official sources, and every page links to them.

The site may earn money from clearly marked affiliate links. That never changes what a calculator shows. See the affiliate disclosure.

How the calculators work

• One set of formulas. Every calculator uses the same tested functions for loan payments, NOI, cap rate, cash-on-cash, DSCR and depreciation, so the numbers agree from page to page.
• Tested math. Automated tests check the formulas against worked examples, including the IRS table for 27.5-year residential depreciation.
• Pre-tax unless stated. Cash flow and returns are before income tax. Pages that touch tax say which rules they use.
• Private by design. The math runs in your browser. Nothing you type is sent to a server or saved.

Data sources

• Property tax by state and county: U.S. Census Bureau, American Community Survey 2020-2024 5-year estimates, tables B25103 and B25077.
• Depreciation and rental income rules: IRS Publication 527 and Publication 946.

What the site does not do

It does not give legal advice. Landlord-tenant rules, rent limits and eviction steps depend on your state and often your city. Where a page mentions a law, it is general information with a link to the official source; check it, or ask a local attorney, before you act.

Corrections

If you find a number that looks wrong, write to hello@mathforlandlords.com with the page and the figure. Confirmed errors are fixed and the page's "last updated" date changes.