About this scientific calculator
Type an expression and get the result: addition, subtraction, multiplication, division, powers (^), modulo (%), parentheses and unary minus, plus sin/cos/tan, asin/acos/atan, ln, log, square root √ and factorial !, with π and e available as constants. Trigonometric functions switch between radians and degrees, and the inverse trig functions return angles in the selected unit.
The engine is a hand-written tokenizer plus the shunting-yard algorithm: expressions are converted to postfix (RPN) and evaluated with the usual precedence and associativity (^ is right-associative, −2² = −4), and omitted multiplication signs such as 3π or 2(3+1) are inserted automatically. Results keep 12 significant digits and switch to exponential notation when very large or small; division by zero, syntax errors and invalid factorials are reported clearly. The last 5 calculations can be clicked to refill the input, and everything runs locally in your browser.