Payas Web Kit · Calculator
Payas Reckoner
A comprehensive multi-mode browser calculator with ten distinct modes — from a simple four-function calculator all the way to matrix operations, graphing, and financial analysis.
id::payas-reckoner · stable
KitPayas Web Kit
PlatformBrowser · Web
Modes10 calculator modes
HistoryLast 100 entries
CurrencyLive rates · cached
ChartsHTML5 Canvas
LicenseGPLv2
Calculator modes
10
Basic to Matrix
History
100
Exportable to .md
Matrix size
8×8
Det · Inv · RREF · LU/QR
License
GPLv2
Open source
10 modes
Calculator modes
Switch modes with Ctrl+M or the mode drawer. Each mode has full keyboard support.
Basic & Scientific
Standard four-function calculator with memory (MC/MR/M+/M−/MS) and history. Scientific mode adds trig, hyperbolic, logarithms, and DEG/RAD/GRAD angle modes.
Graphing
Canvas-based function plotter with pan/zoom, up to 5 simultaneous traces, and a regression overlay. Custom engine — no library.
Financial
TVM (Time Value of Money), NPV/IRR, amortization schedules, and bond pricing — all the tools needed for financial analysis.
Programmable
Custom interpreter supporting LET, FOR, WHILE, IF, PRINT, INPUT — with a step debugger and save/load for programs.
RPN · Programmer · Statistical
HP-style Reverse Polish Notation with 4-level stack. Programmer mode with BIN/OCT/DEC/HEX and 64-bit grid. Statistical mode with distributions and t-tests.
Unit / Currency · Matrix
12 unit categories with live currency rates and favourites. Matrix mode up to 8×8 with det, inv, RREF, LU/QR decomposition, eigenvalues, and cofactor/adjugate.
technical · details
Technical details
| Entry point | payas-reckoner/index.html — multi-file app, static only |
| Stack | HTML5 · CSS3 · Vanilla JavaScript ES2022 |
| Dependencies | Bootstrap 5.3.3 (grid/utilities) · Material Icons (Google) · Google Fonts |
| Storage | localStorage — theme, history (100 entries), currency cache, mode preference |
| Charts | HTML5 Canvas with custom graphing engine — no external charting library |
| Keyboard | Full keyboard navigation in every mode; Ctrl+D theme · Ctrl+H history · Ctrl+M mode drawer |
| Export | Calculation history exportable to .md file |
| Developer | Saman Udayanga Wijesinghe |
| License | GPLv2 (differs from other Payas tools) |