Short answer
These maths tools run entirely inside the web browser: an expression calculator, percentage calculations in five forms, unit conversion across eight families, number base conversion, Roman numerals, numbers written out in words, scientific notation, prime factorisation, greatest common divisor and least common multiple, fraction and ratio reduction, a quadratic equation solver, permutations and combinations, circle geometry, loan repayments, compound interest, a full set of descriptive statistics, and a cryptographically seeded random number generator. Every one of them works on a whole column of values at once rather than a single sum, which is the thing a pocket calculator cannot do.
Write the sum the way you would on paper, and get every line answered.
Pick which percentage question you are asking, then answer forty of them at once.
One number, all four bases, with no rounding at any width.
Break a number down into the primes it is built from.
The greatest common divisor and least common multiple of a whole list.
One fraction, shown four ways.
Paste a column of numbers, get the whole summary.
Numbers in a range you choose, drawn fairly.
Write the unit next to the number and get every other unit back.
MCMXCIV one way, 1994 the other, a whole list at a time.
One number in four forms: decimal, scientific, engineering and E.
Both roots, the discriminant and the vertex, from the equation as written.
All four counts for n and r: ordered or not, repeats or not.
The monthly payment and what the loan costs in total, side by side.
What it grows to, what the interest is, and the effective annual rate.
1234.56 spelled out — in English words or Chinese numerals.
1920:1080 reduces to 16:9; 3:4 = 9:? solves to 12.
One measurement in, all four out.
Several Bézier segments, closed into one shape, out as SVG.
Drag the two control points; the dot underneath shows the easing.
The reason to open a page rather than the calculator already on the phone is volume. One percentage is faster to work out by hand than to type into a form; forty of them are not, and neither is the mean and standard deviation of a column pasted out of a spreadsheet. Every tool here reads line by line, so the answer comes back in the same shape the question went in.
The arithmetic happens on the device, in plain JavaScript, with nothing to download and nothing sent anywhere. That matters less for a sum than for a tax return, a payroll column or a set of clinical measurements — and those are exactly the numbers people paste into a free website without thinking about where they land.
Yes. No account, no daily limit and no paid tier. Your device does the arithmetic, so there is nothing to charge for.
No. Every tool is JavaScript running in your own tab. You can confirm it in the browser's network panel, or by disconnecting after the page has loaded — the tools keep working.
Yes, and that is the intended use. Numbers can be separated by newlines, spaces, commas or semicolons; the tools that work per line read one item per line, and the statistics tool reads the whole block at once.
They use the same IEEE 754 double arithmetic every programming language does, with results rounded to twelve significant digits before display so that 0.1 + 0.2 reads as 0.3 rather than 0.30000000000000004. Base conversion and the least common multiple use arbitrary-precision integers instead, because those routinely exceed what a double can hold exactly.
Yes, once the page has loaded. Nothing here fetches anything.
