This page mirrors the Microsoft Windows calculator in Standard and Scientific modes with keyboard shortcuts, memory keys, and history-free simplicity. Standard mode covers arithmetic, square root, reciprocal, and percent operations; Scientific mode adds trigonometry, logarithms, powers, factorials, and constants such as π and e for quick desk-check math.

Try computing sin(35°) + ln(120) or use MC, MR, M+, and M− to accumulate running totals while budgeting on a laptop without alt-tabbing to the OS app. Toggle DEG/RAD/GRAD when solving physics homework, and switch between Standard and Scientific layouts with the mode button at the top of the widget.

All arithmetic uses decimal.js in the browser for predictable decimal behavior, and state persists in localStorage so refreshes do not wipe half-finished chains. The widget layout remains LTR regardless of site language direction. Use it for quick sanity checks— not safety-critical engineering sign-off where validated tools are required.