Every listing says it's a great deal. Check the math.

Put in the price and rent. Get your real monthly cash flow, what happens if your assumptions turn out wrong, and the most you should offer, with every step shown. We fill in typical numbers for what you don't know.

Built by first-time buyers who wanted a calculator that explains itself. Free, no account needed. Your numbers stay in your browser. Kept free by coffees from people it helped.

Turnkey duplex, fully let

For sale

Asking price
$255,000
Offer $203,500 or less to meet your goals: net yield 1 pt above your loan rate, break-even cash flow, 1.25 DSCR
Seller's yield claim
“10.1% rental yield!”
That's gross. After costs it's 5.6%, and only -0.0% on the cash you put in
Seller's cash flow claim
“Cash flow from day one!”
−$2/mo. A tougher year (rent 10% down, one more empty month, costs up, one big repair): −$756/mo
A listing flyer for a duplex asking $255,000 at $2,140 a month rent, with the seller's claims corrected by the analyzer.

Three questions to answer before you sign anything

Same duplex as above, with typical costs filled in. Every figure on this page comes from the analyzer itself.

What will I actually keep?

Enter the price, rent and interest rate. We fill in typical numbers for the rest, mark each one, and link to how to find yours. Every figure opens up to show the formula with your numbers in it.

Each month, with typical costs filled in

Rent
$2,140
Empty months, averaged out
−$178
Mortgage
−$1,229
Tax, insurance, repairs and management
−$735
You keep
−$2/mo

How much can go wrong?

We ask what you are after, then test what happens if rent comes in lower, prices rise slower or costs run higher over your time frame, and show how much of each thing the deal can take before cash flow hits zero, and tell you what breaks first. You see whether you can carry it before the bank finds out for you.
Your assumptions
−$2/mo
A tougher yearRent 10% down, one more empty month, running costs up, one big repair
−$756/mo
Cash flow hits zero at 1.0 empty months a year, or a loan rate of 6.0%, or rent -0% lower.

What should I offer?

We start from typical goals (cash flow of at least $0, 6% cash-on-cash, 1.25 DSCR) and find the highest price that meets all of them. Change the goals and the number moves. You walk into the negotiation with a number instead of a feeling.

Asking

$255,000

Most you should offer

$203,500

The most you should offer, so that:

  • net yield 1 pt above your loan rate
  • Pays for itself (cash flow $0 or more)
  • 1.25× DSCR

You can also save deals, compare them side by side and export a PDF report to share.

Why we built it

We wanted to buy our first investment property and had no idea what we were doing. Agents, sellers, everyone threw numbers and jargon at us, and nudged us to just sign.

We didn't want to be told it was a good deal. We wanted to understand the numbers ourselves. The calculators we found were black boxes, so we made one that explains itself.

It's free, with no ads and no paywall, and we don't sell your data. Hosting and new features come out of our own pockets. If it helped you, a coffee goes a long way.

The people who built this

Buy us a coffee

Questions we had too

Is it really free?

Yes. Every feature — ROI, cash flow, IRR, what-if tests, the Deal Negotiator, PDF export, and saved deals — is completely free. No credit card, no subscription, no trial that runs out.

Who built this, and why is it free?

A few of us who wanted to buy our first investment property and knew nothing. Everyone pushed numbers and jargon at us, and the calculators we found were black boxes. So we built the one we wished we had. We keep it running ourselves, and some of the people it helps buy us a coffee. If it saved you time or money, you can do the same — if not, no hard feelings.

Do I need to sign up to analyze a deal?

No. The analyzer works with zero friction — no email, no card. You only need an account if you want to save deals across sessions.

Are my numbers stored anywhere?

When you're not signed in, your inputs stay in your browser. We don't send them anywhere. If you sign in and save a deal, only the deals you explicitly save are stored in your account.

How accurate are the calculations?

Every metric (cap rate, cash-on-cash, IRR, NOI, DSCR) uses the standard industry formulas, and we show the full step-by-step computation behind each one — no black boxes. Compare it to your spreadsheet and you'll see the same numbers. For what you don't know yet (closing costs, vacancy, running costs, growth) we fill in typical numbers, mark them clearly, and link to how to find yours. The price, rent and interest rate are always yours to enter.

How is this different from a spreadsheet or a Zillow estimate?

Spreadsheets hide assumptions and don't test what happens if your assumptions are wrong. Listing sites skip vacancy, repairs, and rate changes. The analyzer fills in typical costs, shows how much can go wrong, runs a year-by-year forecast, and tells you the highest price that meets your goals.

Does the analyzer work for properties outside the US?

Yes — it works for any country. Every metric (cash flow, cap rate, IRR, the bad-year check, the Deal Negotiator) is pure math and needs no location data.

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