Verified calculation
The whole schedule, not just a number.
Most calculators hand you one figure and keep the working. These show all of it.
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What is a debt actually costing you?
What the debt payoff calculator produces
$9,400.00 of debt, $600.00 a month
Worked out in your browser · nothing transmitted
- Debt-free in
- 19 months
- instead of 77
- Interest saved
- $5,021.37
- against paying minimums
Every figure above is produced by the calculator itself when this page is built — not written by hand.
What the big comparison sites will not give you
Not a claim about their arithmetic — a claim about their incentives. A site funded by lead generation needs your email and your attention. This one has no backend to send anything to.
Your numbers stay here
There is no server to send them to. No account, no email wall, no analytics attached to what you typed. The claim is structural, not a promise.
Arithmetic you can check
Five formulas reproduce every published figure in your own spreadsheet — including the two where we differ, and by exactly how much.
The document, not the answer
Every period, a chart, a CSV, and a printable schedule with a link back to your exact scenario. Yours to keep and to send on.
Check our arithmetic yourself — five spreadsheet formulas and the SEC's own calculator, about ten minutes.
Calculators
- Debt payoff — avalanche vs snowballCompare both methods against paying minimums. Full month-by-month schedule, chart, CSV and printable report.
- Mortgage overpayment — what an extra payment removesHow much interest and how many years an overpayment takes off, against the contractual schedule. Full amortisation table, chart, CSV and printable report.
- UK early repayment charge — is the charge worth paying?What an overpayment charge costs against the interest the overpayment removes, split into the part your fixed rate guarantees and the part that assumes it holds. Full schedule, chart and CSV.
- Coast FIRE — when saving becomes optionalHow much you need invested today for it to reach your retirement target on its own. Year-by-year projection, chart and export.
Derivations
The arithmetic behind the tools, worked out with real figures.
- How credit card interest is actually calculated — the daily periodic rate, and why 22.99% costs 25.838%.
- Why a 7% return is not 0.583% a month — one division that overstates thirty years by $50,424.
Who writes this
Built by a software engineer, not a financial adviser. That distinction matters and we are precise about it: this site does arithmetic and shows its working. It never tells you what to do with your money.