Math tools
Percentages, fractions, ratios, standard deviation, aspect ratio, random numbers and number base conversion, with the working shown.
12 tools · free · no account · nothing uploaded
All 12 math tools
Percentage Calculator
Work out percentages, increases, decreases and percentage differences with the formula shown for each answer.
Open toolAspect Ratio Calculator
Enter an original size and a new width or height — the other side is calculated to preserve the ratio.
Open toolRandom Number Generator
Pick numbers between a minimum and maximum using the browser's cryptographic random source.
Open toolDice Roller
Roll up to 100 dice of any standard type, add a modifier and see each face plus the total.
Open toolStandard Deviation
Paste a list of numbers to get mean, median, both standard deviations and variance.
Open toolFraction Calculator
Do fraction arithmetic and get the answer simplified to lowest terms with its decimal value.
Open toolAverage Calculator
Paste numbers to get the mean, median, mode, range and sum in one view, with the count and the working shown.
Open toolRatio Calculator
Simplify a ratio to its lowest terms and solve for the missing side at any scale.
Open toolBinary to Decimal
Convert binary numbers to decimal, hexadecimal and octal, with invalid digits flagged.
Open toolPercentage Change Calculator
Work out the percentage change between two numbers, plus the difference and the multiplier, with the formula shown.
Open toolDecimal to Binary
Convert a decimal number to binary, hexadecimal and octal. Enter a whole number and see all three representations, plus the bit length.
Open toolHex to Decimal
Convert hexadecimal values to decimal, binary and octal. Accepts 0x prefixes and both upper and lower case digits.
Open toolWhat these math tools cover
School and spreadsheet maths, minus the spreadsheet. Percentage change, fractions, ratios, averages and standard deviation, plus number base conversion and the small utilities people search for daily: dice, random numbers and aspect ratios. Results are computed with the standard formula and the formula is printed with the answer, so a mark or a quote can be checked step by step.
Common jobs
- Working out a percentage change between two figures
- Simplifying a fraction or scaling a ratio
- Picking a random number for a draw without a bias
Why they run on your device
These pages are static files. The work is done by JavaScript in your tab, so a file or a password never leaves your machine — there is no upload endpoint on this site to send it to. That also means no account, no usage counter and no queue.
Questions
Can I see the formula?
Yes. Calculators that use a formula print it alongside the answer so you can repeat the arithmetic yourself.
Are random numbers really random?
They use the browser's cryptographic generator where the tool needs unpredictability, not Math.random.