Form index
The worksheets.
Last reviewed July 13, 2026
Four worksheets, each built to answer one question and to show its working. They run entirely in your browser — nothing you type is transmitted, logged, or stored, and there is no email gate in front of the results.
Every tool here is derived from the standard published formulas rather than an embedded third-party widget, which means the arithmetic can be audited. It is written out in full on the calculation methodology page, along with the assumptions each tool makes and what it deliberately leaves out. Read that page before you trust a number here for anything that matters.
Mortgage payment & amortization
The monthly payment, the total cost of borrowing, the full month-by-month schedule, and the month your payments start doing more work on principal than on interest.
Form RFI‑01Refinance
Your current loan against a proposed new rate and term — monthly saving, breakeven month, and the lifetime-interest figure that catches a term reset.
Form RVB‑02Rent vs. buy
Net cost of renting against net cost of owning over your horizon, counting equity, selling costs, and the return on the money a renter keeps invested.
Form AFD‑03Affordability
Work backward from income and debts to a price range — and see which ratio is actually binding, because that tells you which lever moves the answer.
A word on what these produce. Every figure is an estimate built on stated assumptions. None is a loan offer, a rate quote, a pre-qualification, or a pre-approval. Your lender's Loan Estimate is the authoritative statement of what a loan will cost you, and where it disagrees with anything here, it is right and this site is wrong.