About PayoffMath
I built PayoffMath because I kept doing the same loan-payoff math by hand — once for my own auto loan, once for a refi on a house I was flipping, once when a friend asked. The math is the same every time. The interesting numbers (interest saved, months shaved off, how a lump sum changes things) are usually one column over from what the lender shows you on the disclosure.
So this is a calculator that shows those numbers, plus short guides that explain what the math is doing. That's it.
Who runs this site
James L. Wu
Finance practitioner & researcher
I've worked in the finance industry for about a decade, mostly around consumer credit, mortgages, and personal loans. I've also done a handful of real-estate flips, which is where I've done the most refinancing math personally. I am not a licensed financial advisor and PayoffMath isn't affiliated with any lender.
What this site does
- A calculator that takes your loan inputs and shows when it actually pays off, with and without extras.
- Short guides on the parts of consumer-loan math that are easy to get wrong (prepayment penalties, biweekly mechanics, lump sum timing).
- A periodic rate-outlook page where I write what I think is happening with the Fed and what that means for borrowing rates.
What it doesn't do
- Give you personalized financial advice. I'm not a fiduciary. Your situation isn't in this calculator.
- Send your loan inputs anywhere. The calculator runs in your browser; nothing leaves your device unless you click the share link.
- Hide affiliate relationships. If we link to a lender for a commission, the disclosures page says so.
- Hide the math. The full formulas + assumptions + what the calculators don't model live on the methodology page.
Contact
Corrections, source pointers, journalist queries, or anything else: admin@payoffmath.com. I usually reply within a few business days.