Willis12C · RPN financial calculator
Loans, cash flows and bonds,
worked to the last digit.
A programmable RPN financial calculator for people who think in a stack. It computes in true 10-digit decimal arithmetic, not binary floating point, and works financial results to about 70 digits before rounding once.
A classic faceplate, drawn in code
A brushed gold band, bevelled keys, gold and blue shifted functions and a seven-segment display. It stays sharp at any size, and on iPhone it fills the screen in landscape.
A complete financial calculator
The math engine has been checked against more than 15,000 independently computed cases.
Time value of money
- Solve for n, i, PV, PMT or FV
- Payments at the start or end of the period
- Odd first periods, simple or compound interest
- Amortization, one payment or a year at a time
Cash flows & bonds
- NPV and IRR with up to 20 groups of cash flows
- Bond price and yield to maturity
- Accrued interest
Depreciation & interest
- Straight line, sum of the years’ digits, declining balance
- Simple interest on 360- and 365-day years
- Percent, percent difference, percent of total
Dates & statistics
- Date arithmetic and days between dates
- Actual or 30/360 basis
- Statistics, weighted mean and linear estimates
Programs & the keyboard
- Keystroke programs of up to 99 lines
- On Mac, type digits and operators directly
- An on-screen key map any time
- Copy and paste the X value
Always where you left it
- Stack, registers, cash flows and programs saved automatically
- Built-in help with worked examples
- No account, no ads, no tracking
- No internet connection needed — Privacy Policy
$3.99. Once.
No subscription, no in-app purchases, no account.
Willis12C will run on Mac and iPhone. It is not planned for iPad, Windows, Android or Linux. Privacy Policy
Ask us anything
Questions about Willis12C, or a calculation you’d like it to handle? Reach out through our support center.
Willis12C is original software. It contains no third-party firmware or ROM, and Lacy Digital Labs, LLC is not affiliated with or endorsed by any calculator manufacturer.