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Zillow Rental Calculators Compared (BiggerPockets, Doorhack, Realy, and More)

Compare Zillow rental analysis tools—web calculators, Chrome extensions, and Realy—on metrics, assumptions, bulk screening, and which fits your investing workflow.

June 4, 2026

"Zillow rental calculator" returns dozens of options—standalone websites, browser extensions, and membership tools. They overlap but solve different parts of the workflow.

Comparison at a Glance

Tool	Where it runs	Bulk Zillow search	Custom assumptions	Cap rate / CoC	Best for
Realy	Chrome + Realy.app	✅ Table + map	✅ Full panel	✅ Both	Ranking entire searches
BiggerPockets Calculators	Web	❌ Manual entry	✅ Moderate	✅ Yes	Learning + one-off calcs
Doorhack / similar extensions	Chrome on Zillow	⚠️ Varies	⚠️ Varies	✅ Often	Quick listing overlays
CashOn / Ostrich / others	Chrome on Zillow	⚠️ Varies	⚠️ Varies	✅ Often	Single-listing screens
Manual spreadsheet	Sheets/Excel	❌ Manual paste	✅ Unlimited	✅ DIY	Custom reporting

Features vary by version; verify on each tool's current site.

BiggerPockets Calculators

Strengths:

Trusted education brand
Multiple calculators (rental, flip, BRRRR, etc.)
Good for learning formulas

Gaps for Zillow browsing:

No native integration—you re-type listing data
No map/table view of a Zillow search result page
Slower for screening 50+ listings

Best use: Learn metrics, verify one deal, complement a browsing tool.

Chrome Extension Calculators (Doorhack, CashOn, etc.)

Strengths:

Metrics appear while you browse Zillow
Faster than web calculators for single listings

Common gaps:

Limited bulk analysis of full search results
Assumption sync across listings may be inconsistent
Fewer report/sharing features

Best use: Casual investors checking a listing someone sent them.

Realy

Strengths:

Search-page analyzer: Rank every listing on a Zillow results page by CoC or cap rate
Unified assumptions: 20% down, 1% closing, 6.5% rate, 2% tax defaults—fully editable
Full metric stack: NOI, cap rate, loaded cap rate, CoC, DSCR, rent/sqft, monthly OpEx + debt
Three surfaces: Search tab, listing mini panel, Realy.app detailed view (synced)
Shareable reports

Limitations:

Zillow only (for now)
Residential 1–4 units (buy-and-hold focus)

Best use: Active investors who browse Zillow daily and need speed + consistency.

What "Good" Looks Like in a Calculator

Whichever tool you use, confirm it models:

✅ Gross rent (editable)
✅ Vacancy
✅ Property taxes (% or $)
✅ Insurance
✅ Maintenance / capex reserve
✅ HOA (critical for condos)
✅ Management fee
✅ Mortgage P&I (not just "payment estimate")
✅ Cap rate AND cash-on-cash (different questions)

Realy includes all of these in calculatePropertyMetrics.

Which Should You Pick?

If you...	Use
Browse Zillow searches weekly	Realy
Analyze one listing from a wholesaler email	Any extension or BP calc
Build LP syndication models	Spreadsheet + Realy for sourcing
Learn investing fundamentals	BiggerPockets + Realy on live listings

Many investors use Realy for sourcing and spreadsheets for final LP packages—not either/or.

Try Realy on a Live Search

Install the extension
Open Dallas Zillow search
Compare your current calculator workflow side-by-side