DoorMeter guide
How to read the card, how every number is calculated, and how to get the most out of DoorMeter.
Getting started
- Add DoorMeter to Chrome from the Chrome Web Store, then pin it: click the puzzle piece in Chrome's toolbar and the pin next to DoorMeter.
- Open a home for sale on Zillow or Redfin. The DoorMeter card appears on the right side of the listing. Drag it anywhere; it remembers where you put it.
- Set your interest rate. Click the DoorMeter button in the toolbar and enter the rate your lender quoted. Until you do, DoorMeter uses 7%.
Zenlist: click the DoorMeter toolbar button and choose "Turn on DoorMeter for Zenlist". Chrome asks once for access to zenlist.com; reload any open Zenlist tab. The card then works on Zenlist listings too.
Works in desktop Chrome on U.S. homes for sale. Rentals, sold homes and listings without an asking price ask you to enter a price.
Reading the card
The score (0–100) sums up how close the deal comes to your targets: 70+ GOOD 40–69 FAIR under 40 WEAK
The four numbers are monthly cash flow, cash-on-cash return, cap rate and DSCR. Each is explained in How the numbers work.
The collapse button in the corner folds the card into a small pill; click the pill to open it again.
- Summary
- The monthly math, top to bottom: rent, vacancy, operating expenses, net operating income, mortgage, cash flow. Below it, the 1% rule and 50% rule checks, break-even rent and the cash you'd need to buy.
- Assumptions
- Every input you can change: price, rent, units, tax, insurance, HOA, down payment, rate, loan term, closing costs, vacancy, maintenance, CapEx and management. The numbers update when you leave a field or press Enter.
- Expenses
- Each monthly expense on its own line, and what share of the rent they take.
- Offer Pro
- The highest price that still meets each of your targets (cash-on-cash, cash flow per door, DSCR), compared with the list price.
- What-if Pro
- Monthly cash flow across interest rates (±2%) and rents (±15%). Red loses money, amber is under $100, green is $100–199, dark green is $200 or more.
- 30-yr Pro
- Cash flow, equity and the return if you sold (IRR) in years 5, 10 and 30, plus the yearly depreciation deduction.
How the numbers work
All amounts are monthly unless a formula says × 12.
| Gross rent | rent per unit × units |
|---|---|
| Effective income | gross rent × (1 − vacancy) |
| Operating expenses | tax + insurance + HOA + utilities + other + maintenance and CapEx (% of gross rent) + management (% of effective income) |
| Net operating income (NOI) | effective income − operating expenses |
| Mortgage | principal and interest on price × (1 − down payment), plus PMI of 0.5% a year when you put down less than 20% |
| Cash flow | NOI − mortgage |
| Cash needed | down payment + closing costs + upfront repairs |
| Cash-on-cash return | cash flow × 12 ÷ cash needed |
| Cap rate | NOI × 12 ÷ price |
| DSCR | NOI ÷ mortgage payment (lenders usually want 1.25 or more) |
| 1% rule | gross rent ÷ price; passes at 1% or more |
| 50% rule | operating expenses ÷ gross rent; passes at 50% or less |
| Break-even rent | the rent at which cash flow is exactly $0 |
The deal score
Each of four results is compared with your target and capped at 100%, then weighted:
- Cash-on-cash vs 8% 35
- Cash flow per door vs $200 30
- DSCR vs 1.25 20
- Cap rate vs 6% 15
With Pro, change the targets in your profile (dashboard → Profiles → "Targets (buy box)"). An all-cash purchase gets full marks for DSCR.
Where the estimates come from
Every number on the card has a chip that says where it came from. Click the chip to see the details.
PAGE read from the listing ESTIMATE filled in by DoorMeter YOU typed by you
- Rent
- The listing's own rent estimate when Zillow shows one for a single home. Otherwise HUD's Small Area Fair Market Rent for the ZIP code and bedroom count (FY2027), or the county figure when the ZIP has none. HUD rents run conservative, so a real rent comp may be higher.
- Property tax
- The county's effective tax rate, or the state's rate when the county has none, × purchase price (Census American Community Survey, 2024), because taxes are usually reassessed after a sale. If the listing shows the seller's last tax bill, you can switch to it.
- Insurance
- The average premium rate for the ZIP code (or state) × price, from U.S. Treasury data (2022). These are homeowner policies; landlord policies often cost more.
- HOA
- From the listing. If a condo or townhouse doesn't list one, the card asks you for it. Other homes that don't list one use $0.
The data ships inside the extension. DoorMeter never sends your listings or numbers anywhere.
Assumptions and profiles
DoorMeter starts every listing from your profile, a saved set of financing and operating assumptions. The default profile, "Buy & Hold (default)", uses:
| Down payment | 25% | Vacancy | 5% |
|---|---|---|---|
| Interest rate | 7% | Maintenance | 5% of rent |
| Loan term | 30 years | CapEx reserve | 5% of rent |
| Closing costs | 3% of price | Management | 8% of income |
| Rent growth | 3% a year | Appreciation | 3% a year |
- On a listing, change anything in the Assumptions tab. On the free plan those changes apply to that listing only.
- Your interest rate can be saved on any plan, from the toolbar button or the dashboard.
- With Pro, save a card's assumptions as a new profile ("Save profile"), keep as many profiles as you like (say, "Columbus duplexes" and "Condos, 10% down") and switch between them in the toolbar popup.
Search badges
On Zillow and Redfin search results, and on Zenlist search results in the tiles view, each home gets a quick estimate under its price, colored like the score. It uses your active profile. Badges never count toward the free monthly limit.
Grey badges mean the search card is missing something the math needs, and DoorMeter won't guess it: no asking price, units not listed (common on multi-family), HOA not listed (common on condos) or no local data. Open the listing for the full analysis.
Scores on the Redfin map (Pro): price pins get a small score bubble, and small dots become rings in the score's color. Zoomed in on a building with several homes for sale, its pin shows the best score among them. A pin with no mark is one DoorMeter can't score from the search (the same reasons as a grey badge). When you move the map, Redfin loads more homes; those get a mark when they're also in the list.
Free plan: one sample badge per search page. Pro: a badge on every home, and scores on Redfin's map. Turn badges off per site in the toolbar popup; that also turns off the map scores.
Saved deals, compare and alerts
- Save deal on the card keeps a listing in your dashboard (toolbar button → "Open dashboard"). Free saves 3 deals; Pro saves unlimited.
- The dashboard lists your deals with price, score, cash flow, cash-on-cash and cap rate. Filter, sort, add notes, and mark each one Watching, Offer made or Passed.
- Compare 2 to 4 deals side by side; a ★ marks the best value in each row.
- Map shows your saved deals as score markers; click one for its details. The filters apply here too. Deals saved before version 1.5 appear after you open their listing once.
- Export CSV and Print summary (PDF) Pro.
- Price-drop alerts Pro: when you see a saved home again on Zillow, Redfin or Zenlist, in its listing or in search results, DoorMeter notes the price. If it's a new low, you get a Chrome notification with the new cash flow and return. DoorMeter never visits listing sites on its own. Turn alerts off in dashboard → Settings.
House hacking
House hacking means buying a home, living in part of it and renting the rest. Flip the card's switch from Buy & hold to House hack, or set a profile's starting strategy to House hack.
- 2–4 units: you live in one unit and rent the others.
- A single home with 2+ bedrooms: you live in one bedroom and rent the others. The rent per room starts as the home's rent split by its bedrooms (an estimate; check local room listings and edit it).
- Buildings with 5 or more units don't fit: home loans for living in the property stop at 4 units.
| Your housing cost | mortgage + mortgage insurance + tax + insurance + HOA + maintenance and CapEx (whole property) + utilities and other costs − rent collected from the other units or rooms (after vacancy and management) |
|---|---|
| Savings vs renting | what renting a similar place would cost − your housing cost (for a room hack, the area's 1-bedroom rent) |
| After you move out | the usual buy & hold numbers with every unit rented (a single home rented whole), on the same loan |
Owner-occupied loans
| Loan | Down payment | Upfront fee (added to the loan) | Mortgage insurance |
|---|---|---|---|
| FHA | 3.5% | 1.75% | 0.55%/yr |
| Conventional | 5% | none | 0.5%/yr until the loan is paid down to 78% of the price |
| VA | 0% | 2.15% | none |
Every value is editable in Assumptions. For an FHA loan on 3–4 units, the card also shows the FHA self-sufficiency check: lenders usually want 75% of the rent from all units, yours included, to cover the full payment.
The house-hack score
- Savings vs renting vs $300 50
- Cash flow per door after you move out 30
- DSCR after you move out 20
With Pro, the Offer tab finds the highest price that still meets each house-hack target, What-if shows your housing cost across rates and rents, and 30-yr has you live there first and rent afterwards. "Move out after (years)" starts at 2. While you live there, the 30-year IRR counts what you save vs renting as your return.
BRRRR
BRRRR means buy, rehab, rent, refinance, repeat: you buy a home that needs work, fix it up, rent it out, then refinance against its higher value to pull your cash back out. Flip the card's switch to BRRRR, or set a profile's starting strategy to BRRRR.
The card asks for two numbers first. DoorMeter never guesses the rehab budget or the value after repairs: no public data gives them, so they come from you (and your contractor and agent).
| Purchase loan | Cash, or hard money: 90% of the price and 100% of the rehab at 12% interest-only, plus 2% in points |
|---|---|
| Refinance at month | 6 |
| Refinance loan | 75% of the value after repairs |
| Refinance rate | your interest rate + 0.5%, 30 years |
| Refinance closing costs | 2% of the new loan |
| Cash in | price + closing costs + rehab + holding costs (tax, insurance, HOA, utilities, other costs and any hard-money interest until the refinance, with no rent) − what the hard-money lender pays + points |
|---|---|
| Cash out | refinance loan − hard-money payoff − refinance closing costs |
| Cash left in the deal | cash in − cash out (zero or less: all your cash back) |
| After the refinance | the usual buy & hold numbers on the new loan; cap rate and the 1% rule use price + rehab, and cash-on-cash uses the cash left in (∞ when none is left in) |
70% rule: price + rehab is at most 70% of the value after repairs. The card shows it as a check next to the 1% and 50% rules; it isn't part of the score.
The BRRRR score
- Cash back vs 100% 40
- Cash flow per door after the refinance 35
- DSCR after the refinance 25
With Pro, change "Cash back at least" and the 70% rule in your profile's targets. The Offer tab finds the highest price that still gets your cash back, What-if shows the cash left in if the rehab or the value after repairs comes in different, and 30-yr starts at the refinance with the cash left in as your investment. Search badges for a BRRRR profile show the buy & hold estimate, since a search result has no rehab budget.
Free, Pro and your license
- Free analyzes 5 listings a month. Reopening a listing you already analyzed this month is free, and the count resets on the 1st.
- Pro ($5/month or $49 once) removes the limits. See pricing.
- Activate: after you buy, Polar emails your license key. Click the DoorMeter toolbar button, paste the key into "License key" and press Activate.
- Browser limit: a key works on up to 2 browsers. With Chrome sync on, it follows your Google account to every Chrome you sign in to, and each one uses a slot.
- New computer: in the old browser, toolbar button → "Remove license key…" (with sync on, this removes it from all your synced Chrome browsers), then activate on the new one. Lost access to the old one? Ask support to reset your slots.
- Manage or cancel: toolbar button → "Manage subscription" opens your Polar customer portal. Monthly Pro stays on until the end of the period you paid for. See the refund policy.
- Offline: DoorMeter checks your key about once a day. If it can't reach the license server, Pro keeps working for up to 7 days.
Troubleshooting
The card doesn't appear
Make sure you're on a single home's page (not search results), and that "Card" is on for that site in the toolbar popup. If the page loaded oddly, reload it.
The card asks me for a price
The listing has no asking price (off market, sold, auction, or a rental). Type the price you'd pay and press Analyze.
Zillow shows "Press & Hold"
That's Zillow checking for bots. Complete it and reload the page; the card will read the listing again.
A number looks wrong
Click its chip to see where it came from, then type your own number in Assumptions. If DoorMeter read the page wrong, use Report broken page at the bottom of the card. You'll see exactly what will be sent first: the page address (without anything after a ?), its structure, the listing ID, your browser version and your note, never your numbers or saved deals.
"That key is expired, refunded, or already active on too many devices"
Your key is on 2 browsers already, it has expired (for example a cancelled monthly plan), or the purchase was refunded. With Chrome sync on, removing the key in one Chrome removes it from every Chrome signed in to the same Google account, so to free a slot, turn off extension sync on the browser you don't use and remove the key there, or contact support to reset your slots.
Still stuck? Email support@doormeter.com.
DoorMeter's numbers are estimates, not financial advice. Check them with your lender, insurer and local professionals before you buy.