Scientific Calculator

Type a whole expression and hit equals — this respects order of operations, so 2 + 3 × 4 gives 14, not 20. That sounds obvious, but a lot of on-screen calculators evaluate as you go and get it wrong. This one reads the entire expression, parses it properly, and only then computes, so parentheses, exponents, and precedence all behave the way they do on paper.

It covers the usual scientific set: trig and inverse trig (with a DEG/RAD switch), natural and base-10 logs, square and cube roots, powers, e^x and 10^x, absolute value, factorial, and the constants π and e. There's memory (MC/MR/M+/M−) and a running history of your last calculations so you can glance back at what you entered.

You can click the buttons or just type — the full keyboard works, including Enter to evaluate, Escape to clear, and Backspace to delete. Degree mode is the default, which is what most people want for everyday trig; flip to RAD when you're doing calculus or working in radians.

Expressions are tokenized and converted to Reverse Polish Notation with the shunting-yard algorithm, then evaluated on a stack. That's what enforces correct precedence and associativity: exponentiation is right-associative (2^3^2 = 512), unary minus sits between multiplication and exponent (so −2^2 = −4 and 3×−5 = −15), and parentheses group as expected. It deliberately does not use JavaScript's eval() — partly for safety, partly because it needs operators JS doesn't have, like factorial and degree-mode trig.

Trig functions convert through radians internally; in DEG mode sin(30) returns exactly 0.5 rather than 0.988. Results are cleaned up to about 12 significant figures, which erases floating-point noise (sin(π) shows 0 instead of 1.2e-16) while keeping genuinely tiny values intact. Very large or very small magnitudes switch to exponential notation.

Domain errors are caught and shown rather than returning NaN: log and ln require positive input, asin/acos need a value in [−1, 1], sqrt needs a non-negative number, division by zero is flagged, and factorial requires a non-negative integer (values above 170! overflow to Infinity in double precision). Everything runs locally in your browser.

Against a phone's built-in calculator, the main difference is the visible expression line: you can see and edit the whole thing before evaluating, instead of trusting an invisible running total. Against a full computer-algebra system like Wolfram Alpha, this is intentionally simpler — no symbolic math, equation solving, units, or graphing. It computes numeric expressions, and does that part correctly.

Reach for a CAS when you need to solve for x, simplify algebra, or work with units. Use this for the common case: evaluating a real numeric expression with functions and precedence, quickly, with a history you can scroll back through.