Methodology

Methodology & disclaimer

Where the numbers come from

Every headline figure is copied from an official government source: a rent board page, a housing department bulletin, an agency notice or the ordinance itself. For each jurisdiction we store the source URL, the date we fetched it, and a short verbatim quote. Our verification script re-reads a saved copy of each page and fails if the quote (and the figure) is no longer there.

Some California entries also cite the California Attorney General's local rent cap chart for coverage dates. Where a city's own page disagrees with that chart (Berkeley's cap was lowered to 5% by Measure BB, for example), we follow the city.

Charts

Every bar, marker and column is drawn from the same data file as the text, and each chart lists its official source. History charts appear only where an agency publishes earlier figures; each point is stored with the source and the exact line it was copied from, and the verification script checks it against our saved copy of that page. Where a place has no official history we could read, we don't draw one.

CPI-based formulas

Many caps are a share of the change in the Consumer Price Index. Where it helps, a page shows the index values from the U.S. Bureau of Labor Statistics public API (api.bls.gov, not seasonally adjusted) and the formula applied to them. Agencies may use different months, annual averages or rounding, so these are cross-checks only. The headline is always the published figure.

When we can't confirm a figure

If we can't read a current official figure (the page hasn't been updated, a table didn't load, or the site blocks automated reading), the page says unconfirmed, shows the last official figure and its dates, and leaves the calculator percentage blank. As of October 18, 2026 that applies to West Hollywood, Newark. Places with no rent cap at all (such as Minneapolis) say so plainly instead.

ZIP code lookup

The city finder matches a ZIP code using the U.S. Census Bureau's 2020 ZIP Code Tabulation Area (ZCTA) relationship files, which say how much of each ZCTA's land falls in each city, town and county. We list every place we track that covers at least 1% of a ZCTA. ZCTAs approximate postal ZIP codes and often cross city lines, so the finder shows every match plus the state-law page and asks you to pick the city your address is actually in. The optional "use my approximate location" button asks our own server for the city and ZIP Cloudflare estimates from your internet connection; it isn't GPS, it can be wrong, and we don't store or track it.

Dates

"Last checked" is the date we last fetched the official page (Pacific time). "Next change" is the date set by law or the agency's usual schedule, not a promise that a new figure will be published that day.

What the calculator does

It multiplies your current monthly rent by the selected percentage, applies any dollar ceiling (for example Santa Monica's $70) and rounds down to the cent. It ignores banking, pass-throughs, surcharges, petitions and whether your unit is covered. It runs in your browser; the rent you type is never sent anywhere.

All sources