Know what the loan actually costs.
A loan calculator and tracker for iPhone and Mac. Every payment to the cent, extra principal modelled honestly, and a payoff order you can check rather than trust.
Where it stands
In testing on TestFlight, now building and installing as ForjLoan on both platforms. Every calculation rule has a written acceptance test — 135 for the engine, 79 for the app on each platform — because the arithmetic is the whole product.
What it does
| Amortization | Every payment in the schedule, to the cent. Exact decimal arithmetic, not floating point — a rounding error is a wrong answer, not a small one. |
| Extra principal | Model a one-off overpayment or a standing one, and see exactly how much interest you never pay and how many payments disappear. |
| Payoff order | Avalanche and snowball, side by side across several debts, so the cheaper plan and the more motivating plan are both visible. |
| Both devices | Start on the iPhone, finish on the Mac. Syncs over your own iCloud account — there is no ForjLoan account to make. |
| Stays private | Your balances are yours. Nothing is uploaded anywhere we can read, and the app can be locked behind Face ID. |
Why it exists
Loan maths is simple enough that everyone assumes it is right, and subtle enough that it often isn't. Building this one turned up a payment schedule a day early, a phantom extra-principal row, a one-cent truncation compounding over thirty years, and an avalanche/snowball comparison with the two strategies backwards — all in code that looked perfectly reasonable. The fix for that class of bug is checking every rule against a written criterion, which is what this app is built on.
iPhone and Mac · iOS 17 or later, macOS 14 or later · native SwiftUI
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