How to use this calculator
Click buttons or use your keyboard. The display shows the live expression on top and the running result below — there's no separate "evaluate" step beyond the = key (which copies the result back to the input for chaining).
Simple vs Scientific mode
Simple mode keeps only basic operations (+ − × ÷). Scientific mode reveals trigonometry (sin, cos, tan), logarithms (log, ln), exponentials (exp), powers (x^y, x²), roots (√, ∛), factorial (x!), absolute value, π and e.
Angle mode
Trigonometric functions respect the DEG / RAD toggle in the top right. Switch to RAD when working with radians (e.g. sin(π/2) = 1).
Keyboard shortcuts
- Numbers, operators, parentheses — type as usual
- Enter or = — chain the result into the next operation
- Backspace — delete the last character
- Escape — clear all (AC)
Privacy
Calculations happen entirely in your browser using a custom expression parser (no eval) — your input is never sent to any server.
Frequently asked questions
Why does sin(90) give 0.893 instead of 1 on my calculator?
Your calculator is in radians mode. In radians, sin(90) ≈ 0.894 because 90 radians is not 90 degrees. The value sin = 1 corresponds to 90° = π/2 ≈ 1.5708 radians. To get 1, switch to DEG mode and enter sin(90), or type sin(π/2) in radian mode. Wrong angle mode is the single most common trigonometry error in practice, and has caused real engineering failures.
When should I use ln instead of log?
Use ln (base e) for continuous growth or decay: radioactive half-life, chemical kinetics, continuously compounded interest, differential equation solutions. Use log (base 10) for perceptual magnitude scales: decibels, pH, Richter seismic magnitude. Use log₂ in computer science: O(log n) algorithm complexity, binary trees, Shannon entropy. The choice follows the underlying phenomenon, not personal convention.
How does my calculator handle decimal precision?
It uses IEEE 754 double precision (64-bit, the JavaScript standard), giving 15 to 17 significant digits. Some decimal fractions like 0.1 have no exact binary representation, hence 0.1 + 0.2 = 0.30000000000000004. For financial calculations requiring exact decimal arithmetic, work in integers (cents) and convert to monetary units only at display time, or use a library such as Decimal.js.
What is the difference between PEMDAS and BIDMAS?
Two mnemonics for the same universal rule. PEMDAS (American) stands for Parentheses, Exponents, Multiplication, Division, Addition, Subtraction. BIDMAS (British) stands for Brackets, Indices, Division, Multiplication, Addition, Subtraction. The rule is identical. Key point: Multiplication and Division share equal priority and are evaluated left to right, so 12 ÷ 4 × 3 = 9, not 1. The order of letters in the acronym does not imply M outranks D.
How do I calculate 50! quickly without overflow?
50! ≈ 3.04 × 10⁶⁴, well below IEEE 754's max of ≈ 1.8 × 10³⁰⁸ — no overflow. Precision degrades above ~21! since large integers cannot be represented exactly as doubles. For an approximation, Stirling's formula gives ln(n!) ≈ n·ln(n) − n + ½·ln(2πn). For exact values, Python's native integers are arbitrarily large; Java's BigInteger works too. In combinatorics problems, working entirely in log-space keeps you within normal floating-point range until the final step.
