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Keystone

About Keystone

We build the real estate calculators we always wanted: fast, honest about their assumptions, and clear about the math.

Why we exist

Most real estate calculators online are cluttered, opaque, or quietly built to sell you a loan. You enter numbers, a figure comes out, and you have no idea how it was produced. That is a bad way to make one of the largest financial decisions of your life.

Keystone takes the opposite approach. Every calculator shows its formulas, explains its assumptions, and updates instantly as you change inputs, so you can see exactly which variables drive a deal.

Our standards

  • Transparent math. Each tool publishes its methodology and a worked example you can check by hand.
  • Built for the US market. We model US lending conventions — fixed-rate amortization, typical loan-to-value limits, FHA and conventional program rules, and IRS depreciation schedules.
  • Private by design. Calculations run in your browser. We never see the numbers you enter.
  • Reviewed and maintained. We review formulas and program limits regularly and date every update.
  • Independent. Advertising keeps the tools free, but advertisers have no influence over our formulas or content.

Who it's for

Rental investors underwriting their next BRRRR deal, first-time buyers comparing loan programs, flippers working out a maximum offer, and agents who want a clean tool to share with clients.

Get in touch

Found an error, or want a calculator we don't have yet? Contact us. We read everything.