Basic Calculator
Free online four-function calculator with full keyboard support and a running history of every operation. Add, subtract, multiply, divide, percent, and sign-flip — works on any device.
How to Use
- Click the on-screen keys or use your physical keyboard — both work simultaneously.
- 0–9, +, −, *, /, decimal point, and Enter (=) all work directly from the keyboard.
- Press 'C' or Esc to clear the display. Backspace removes the last digit.
- The "%" key converts the displayed number to a percentage (divides by 100).
- The "±" key flips the sign of the displayed number.
- Every completed operation appears in the History panel for reference and copy-paste.
Keyboard Shortcuts
A Brief History of the Calculator
Mechanical calculators date back to Wilhelm Schickard (1623) and Blaise Pascal's Pascaline (1642), but practical desk calculators arrived only with Thomas de Colmar's Arithmometer (1851), the first machine reliable enough to enter widespread office use. By the late 19th century, mechanical adding machines from Burroughs, Felt & Tarrant, and others had become standard equipment in banks, insurance companies, and government offices. They were heavy, noisy, and required practiced operators — but they were 100× faster than a human with pencil and paper.
The electronic era began with the Casio 14-A in 1957 (a desk-sized relay calculator) and accelerated through the 1960s with transistors. The first handheld electronic calculator was Texas Instruments' Cal-Tech in 1967. The 1970s saw the rapid commoditization of pocket calculators — prices dropped from hundreds of dollars to under $10 within a decade — and by the 1980s the four-function calculator was a free promotional giveaway. Scientific and financial calculators followed similar curves.
The browser-based calculator you're using now is a direct descendant of the Cal-Tech, running entirely on the same JavaScript engine that handles every other web page. The display, button layout, and key bindings track those of the dominant 1970s desktop calculators almost exactly — the design solved the problem so completely that 50 years of UI evolution have hardly touched it.
About This Calculator
This calculator implements the classic four-function model: numbers and operators are processed left-to-right, with each new operator committing the previous result. The display shows up to 15 significant digits (JavaScript double-precision); larger or more precise numbers should use the Big Number Calculator. The history panel records each completed operation for reference.
Everything runs entirely in your browser; no calculations are transmitted, logged, or stored. Once loaded, the calculator works offline. Keyboard support is comprehensive — you can use this without ever touching a mouse, which also makes it accessible to assistive technology users.
Frequently Asked Questions
Why doesn't this calculator follow order of operations?
It's a 'four-function' calculator — operations are evaluated left to right, like the desk calculator on your kitchen counter. 2 + 3 × 4 returns 20, not 14, because each new operator commits the previous result. If you need order of operations (PEMDAS/BODMAS), use the Big Number Calculator or any expression-based tool that parses 2 + 3 × 4 as 14.
Is the result accurate to many decimal places?
JavaScript uses 64-bit IEEE 754 floating-point arithmetic, which gives about 15–17 significant decimal digits. Common surprises: 0.1 + 0.2 displays 0.30000000000000004 because 0.1 has no exact binary representation. For decimal-exact arithmetic (financial reporting, large numbers), use the Big Number Calculator instead.
Does the calculator work offline?
Yes. Once the page is loaded, all computation runs in your browser. You can disconnect from the internet and the calculator continues to work. The site uses a service worker that caches the calculator on first visit.
Are my calculations stored or transmitted?
No. Every keystroke and result is processed locally by JavaScript and is never sent to a server. Refresh the page and the history is gone — there is no backend record of what you computed.
How does the percent key work?
Pressing % divides the currently displayed number by 100. Useful for chaining: type 250 + 8 % to add 8% to 250 (the % converts 8 to 0.08, the calculator then computes 250 + 0.08 = 250.08, which isn't typically what you want — for true percent-of-base, use 250 × 1.08). Different desk calculators behave slightly differently here; the bare-divide-by-100 behavior is the most predictable.
What's the largest number it can handle?
Up to about 1.79 × 10<sup>308</sup> (the IEEE 754 double-precision maximum). Beyond that, the display shows Infinity. Negative overflows behave the same way. For arithmetic on integers larger than 2<sup>53</sup>, precision is lost — use the Big Number Calculator for those.
Common Use Cases
Quick everyday math
Add up grocery prices, divide a check, compute a tip without leaving your browser tab.
School and homework
A simple, distraction-free calculator that won't accidentally let you cheat on order-of-operations problems.
Office and spreadsheets
Sanity-check a formula before pasting it into Excel or Google Sheets.
Programming side calculations
Quick byte-size or memory-footprint calculations while reading documentation.
Field work without a calculator
When you need a calculator and your phone is out of reach but a browser is open.
Accessibility
Full keyboard support means the calculator works for users who can't or don't want to use a mouse.
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