RentalMath
Rental property analysis, from address to underwriting
What the app does, where every number comes from, and how the estimates are built.
On This Page
RentalMath turns a street address into a decision. Type one in and it pulls neighborhood demographics, hazard exposure, market rents, and comparable sales, screens the deal against the numbers, then hands the whole thing to a full pro forma calculator you can adjust line by line. It runs in the browser, installs as an app, and works offline once loaded.
1The three steps
- 1. Neighborhood intelligence
- Income, population, tenure mix, vacancy, home values, and rent levels for the property's Census tract and ZIP, plus FEMA hazard risk, walkability, nearby schools, and amenities within walking distance.
- 2. Deal screening
- A fast pass on whether the deal is worth modeling: estimated value and rent with a low-to-high range, comparable sales and rentals, projected cash flow, and the assumptions behind each. Every headline number carries a chip naming the source that produced it.
- 3. Full pro forma
- Purchase and financing terms, income, operating expenses, capital reserves, and exit assumptions — producing cash flow, cap rate, cash-on-cash return, ROI, IRR, DSCR, amortization, and multi-year equity and appreciation projections.
2Where the numbers come from
RentalMath does not invent estimates or resell a single vendor's feed. It composes 14 public and commercial sources, and tells you which one answered for each figure:
- US Census Bureau — American Community Survey tract demographics, income, home values and property-tax ratios; the public geocoder; and the Building Permits Survey for construction costs.
- Bureau of Labor Statistics — Consumer Price Index for rent of primary residence, used to trend rents.
- HUD — Fair Market Rents and Small Area FMRs by bedroom count.
- FEMA — National Risk Index expected annual loss and hazard exposure by tract.
- FHFA — House Price Index at ZIP level for appreciation history.
- FRED, Federal Reserve Bank of St. Louis — the current 30-year fixed mortgage rate, so financing defaults track the real market.
- Zillow Research — Home Value Index, Observed Rent Index, median sale price, and sale-to-list ratio.
- OpenStreetMap — geocoding via Nominatim and nearby amenities via Overpass.
- Walk Score — walkability for the coordinates.
- Urban Institute — Education Data Portal school directory.
- NAIC — state average homeowners insurance premiums.
- Lincoln Institute of Land Policy — effective property-tax rate ratios between rental and owner-occupied property.
- County assessor records — land-use classification used to identify property type.
- RentCast — property-level valuation, rent estimate, comparable sales and rentals, active list price, and tax records for signed-in users.
3How the estimates are built
Value and rent resolve through a waterfall, strongest source first. For a signed-in user, a property-level automated valuation model estimates that address, and an active listing price takes precedence over the model when the home is on the market. Without property-level data, RentalMath falls back to an area-level ensemble blended from ZIP and tract indices — an honest description of the neighborhood, not of the individual house, and labeled as such rather than presented as a property valuation.
Operating costs are modeled rather than guessed at a flat percentage. Property tax starts from the actual last tax bill where records exist, trended forward and adjusted for non-owner-occupied assessment. Insurance is built from an estimated replacement cost, scaled to state premium data and adjusted for local hazard risk. Both fall back to broader averages when the specific inputs are unavailable, and both tell you which rung answered so you know how much weight to give it.
4Frequently asked questions
Is RentalMath free?
Yes. Neighborhood analysis, deal screening, and the full pro forma calculator are free, with no account required. Signing in is free too and additionally unlocks property-level valuation, rent, comparable sales, and tax-record data for the specific address you analyze, plus optional cloud sync across your devices.
Where does the data come from?
From 14 public and commercial sources: the US Census Bureau (American Community Survey, geocoder, and Building Permits Survey), Bureau of Labor Statistics CPI rent, HUD Fair Market Rents, the FEMA National Risk Index, the FHFA House Price Index, FRED mortgage rates from the Federal Reserve Bank of St. Louis, Zillow research indices, OpenStreetMap, Walk Score, the Urban Institute Education Data Portal, NAIC insurance premiums, the Lincoln Institute of Land Policy, county assessor land-use records, and RentCast for property-level data.
How accurate are the rent and value estimates?
It depends on which source answered, and RentalMath labels that on every number. Signed-in analyses use a property-level automated valuation model for the specific address, reported with a low-to-high range. Without that, estimates fall back to an area-level ensemble blended from ZIP and tract indices, which describes the neighborhood rather than the individual property. Both are starting points for underwriting, not appraisals — verify against real comps and your own quotes before making an offer.
How is property tax estimated?
When the property's actual tax record is available, RentalMath uses the last billed amount trended forward by the local growth rate, adjusted for the fact that non-owner-occupied properties are often assessed differently. In California it instead applies roughly 1.15% of price, because Proposition 13 reassesses at sale. Otherwise it derives an effective rate from Census tract data. The calculator shows which method produced the number, and you can overwrite it with your own figure.
How is insurance estimated?
RentalMath estimates a replacement cost from the building's square footage and local construction costs derived from the Census Building Permits Survey, then scales the state average homeowners premium published by NAIC to that replacement cost and adjusts it by the FEMA National Risk Index expected-loss rate for the tract. Two-to-four unit buildings get a per-unit multiplier. It is an estimate, not a quote — replace it with a real quote when you have one.
What metrics does the calculator produce?
Monthly and annual cash flow, capitalization rate, cash-on-cash return, total ROI, internal rate of return, debt service coverage ratio, net operating income, loan amortization, and multi-year appreciation and equity projections. It supports long-term rentals, BRRRR, fix-and-flip, and multifamily deals.
Does RentalMath work offline?
Yes. It is an installable progressive web app, so the calculator, your saved deals, and all legal documents work with no connection. Live lookups — geocoding, neighborhood data, mortgage rates, and property data — need an internet connection, and recent analyses are saved on-device alongside your deal.
Does RentalMath store my deals on a server?
Not by default. Deals are stored locally in your browser. If you sign in, they sync to your private cloud account so they are available on your other devices; the cached analysis data stays on-device and is never uploaded. Sharing a deal creates a link that carries the deal in the URL or in a short-link record you can let expire.
RentalMath is a calculator, not financial advice, and its outputs are estimates that depend on the assumptions you enter. Verify every figure independently before making an investment decision. See the Financial Disclaimer, Terms of Use, Privacy Policy, and the full list of data sources and third-party services.