CalculatorOnline.xyzArithmetic that stays on the desk
When you need a calculator online, the useful part is often not a catalog of specialized formulas. It is a place to type a short expression, inspect what the machine understood, keep the answer beside the previous line, and continue. CalculatorOnline.xyz is built around that running-desk habit.
The scratchpad accepts addition, subtraction, multiplication, division, decimal numbers, parentheses, unary negative signs, and one explicit postfix percent rule. A strict tokenizer and parser read the expression. JavaScript eval, Function, remote APIs, and guessed corrections are not part of the design. Every completed line stays only in current page memory until a reset, refresh, or closed tab removes it.
Type first or use the controls
The core page supports ordinary keyboard symbols: +, -, *, /, (, ), ., and %. The interface may display multiplication and division as × and ÷ after normalization. Buttons provide the same tokens for touch or pointer use. Enter evaluates. Backspace removes one typed character. CE removes the current numeric entry when possible. C clears the active expression and error state but leaves the memory register until MC or a page refresh.
The parser ignores ordinary spacing but rejects commas, variables, currency symbols, exponent notation, implicit multiplication, and unrecognized characters. 2(3+4) therefore reports a missing operator instead of silently becoming multiplication. An error includes the character position and a short expected-token message.
The first screen says plainly that this is a local arithmetic scratchpad. It does not upload the expression, create an account, save history, or claim to be a financial, medical, tax, legal, or engineering authority.
Percent has one visible meaning
Percent keys differ across physical calculators, so this site does not imitate a contextual brand convention. Here % is a postfix operator that divides the immediately preceding number or parenthesized value by 100. 10% becomes 0.1. 200 × 10% becomes 20. 200 + 10% becomes 200.1, not 220.
That rule is shown beside the keypad and repeated in percent-related results. To add ten percent of 200, enter 200 + (200 × 10%). This looks longer, but it makes the intended base explicit and keeps the parser deterministic.
Worked example: continue from a visible tape
Suppose a workshop buys three material packs at 18.75 each and receives a 12.50 credit. Enter (3 × 18.75) - 12.50. The normalized expression remains visible. The parser resolves the parenthesized product first, producing 56.25, then subtracts 12.50 for 43.75.
After evaluation, the line appears on the running tape with the input, normalized form, result, and a compact order summary. Press M+ to add 43.75 to the memory register. A second line, 8.25 × 2, produces 16.50. MR can insert the stored memory value into a new expression without using a remote history service.
The tape is not bookkeeping. Refreshing the page clears it, and the site does not attach a date, identity, receipt, or audit guarantee. Copy any line you genuinely need into an appropriate record system.
Exact entered decimals, bounded display
Finite decimal tokens are converted to integer coefficients and powers of ten, then carried through a reduced rational representation. This avoids using binary floating-point as the source of arithmetic truth for the supported grammar. Division can produce a non-terminating decimal, so the interface shows an exact fraction when useful and a decimal rounded to a declared maximum of 12 places.
Input length, token count, parenthesis depth, and numerator or denominator size are bounded so a browser tab remains responsive. When a limit is reached, the page returns an error rather than truncating silently. These are product constraints, not mathematical limits.
Choose a narrower tool when the trace matters
The main scratchpad is for mixed expressions. Specialized pages expose a different part of the arithmetic. Addition shows ordered subtotals. Subtraction shows running differences. Multiplication shows partial products. Division shows a multiplication check. The order-of-operations page reveals precedence stages, while the parentheses page focuses on matching groups and inner values.
Memory and tape have dedicated rehearsals because state is often harder to understand than the final number. Rounding, remainder, and reciprocal pages state their own conventions rather than inheriting an invisible button behavior.
Limits of the calculator
The site does not support variables, equations, complex numbers, units, currencies, matrices, graphing, statistics, scientific functions, implicit multiplication, locale-specific decimal commas, or arbitrary precision output. It does not verify the real-world meaning of an expression. A correctly parsed number can still come from a wrong assumption or inappropriate formula.
Use reviewed domain tools and qualified judgment for consequential decisions. Keep original source data and independent checks when a result affects money, safety, health, legal rights, or professional work.
Scratchpad questions
Does the page save my tape?
No. Tape and memory exist only in current page memory and disappear on refresh or closure.
Is eval used to calculate expressions?
No. The calculator uses a tokenizer, recursive-descent parser, and rational arithmetic engine in the current page.
Why does 200 + 10% equal 200.1 here?
Because postfix percent always divides its operand by 100. The site does not copy contextual percent behavior from a physical calculator.
Can I paste a long spreadsheet formula?
No. Only the documented basic grammar and bounded input size are accepted.
Put the next line on the tape
Select Open the online arithmetic scratchpad, type a short expression, read the normalized form and order summary, then keep or clear the local line. If the expression has one narrower purpose, move to its dedicated tool for a more specific trace.