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Numbers

Number utilities: spell out amounts in words, convert Roman numerals, switch between bases, calculate percentages and check primes, one value per line.

A/B test significance calculatornewCalculate conversion rates, lift and statistical significance across A/B test variants.
ASCII bar chart generatornewTurn label/value pairs into a monospace bar chart made of text characters.
BIC/SWIFT code validatornewCheck that a BIC/SWIFT code is well-formed and break it into bank, country, location and branch.
Bill splitternewWork out who owes who from a shared list of expenses, with as few transfers as possible.
Birth number validatorCheck a Slovak or Czech birth number and see the date of birth, age and sex it encodes.
Bitwise calculatornewRun AND, OR, XOR, NOT and bit shifts on two numbers and see the result bit by bit.
Business days calculatornewCount business days between two dates, or add business days to a date, skipping weekends and holidays.
Byte unit converterConvert data sizes between B, KB, MB, GB and TB in decimal or binary units.
Campaign cost calculatornewTurn a list of ad campaigns into CPC, CPM, CTR, CPA, conversion rate, ROAS and margin, computed instantly in your browser.
Credit card number checkerCheck card numbers against the Luhn checksum and detect the scheme — a developer tool for test numbers, not a card verifier.
Date difference calculatorCount the days, weeks, months and years between two dates, with weekdays and weekends.
Duration calculatorAdd up a list of durations and see the total in hours, minutes and seconds.
EAN and UPC validatornewCheck the check digit of EAN-13, EAN-8, UPC-A and UPC-E barcodes, or complete a missing one.
EU VAT number validatornewCheck the format and check digit of European VAT numbers, per country.
Even / odd splitterSeparate even and odd numbers instantly from any text.
Excel column converternewConvert a spreadsheet column number to its letter, or a column letter back to its number.
Factorial calculatorCompute factorials instantly, from 0! to 500! with exact results using BigInt.
Fibonacci generatorGenerate Fibonacci sequences of any length with your choice of starting values and formatting.
Fraction converterConvert between fractions, decimals and percentages, one value per line, with exact simplification.
GCD and LCM calculatorFind the greatest common divisor and least common multiple of two or more integers.
Grade calculatornewTurn a list of students and points into percentages and grades on your own scale.
IBAN validatorCheck IBANs against the official country lengths and the mod-97 checksum — catches typos before a payment, entirely in your browser.
IMEI validatornewCheck an IMEI's Luhn checksum and split it into TAC, serial number and check digit.
Inline math evaluatorFind arithmetic expressions ending in "=" in your text and fill in the answer.
ISBN validatornewCheck ISBN-10 and ISBN-13 checksums, convert between formats, and format with hyphens.
ISIN validatornewCheck whether an ISIN’s country prefix and check digit are valid.
ISO 8601 duration converternewConvert ISO 8601 durations like PT1H30M to seconds or readable text, and back.
Loan payment calculatornewCalculate the monthly payment and full amortization schedule for a loan.
Locale number formatternewFormat a list of numbers as currency, percentages or units, following the rules of any language locale.
Meeting cost calculatornewCalculate the true cost of a meeting from attendee count, hourly rates and duration.
Multiplication tableGenerate a multiplication table for any number, perfect for learning or reference.
Number base converterConvert numbers between any bases from binary to base 36, one per line.
Number sequence generatorGenerate a list of numbers from a start to an end value with any step.
Number to ordinalReplace integers in text with their English ordinal forms (1st, 2nd, 3rd, etc.).
Number to wordsWrite numbers out in words in six languages, with an option for euro amounts.
Percent calculatorCalculate a whole list of percentage expressions at once, one per line.
Percentage calculatorWork out X % of Y, percentage share, percentage change and discounted prices, with the formula shown.
Percentage changeInstantly calculate the percentage change from one value to another.
Prime number checkerCheck whether numbers are prime, see their prime factorization and the next prime.
Recipe scalernewScale ingredient quantities in a recipe up or down for a different number of servings.
Roman numeral converterConvert numbers to Roman numerals and Roman numerals back to numbers, one per line.
Round numbersRound every number in your text to a specified number of decimal places.
SMPTE timecode converternewConvert between SMPTE timecode, frame numbers and seconds at any broadcast frame rate.
Sort numbersSort a list of numbers by numeric value, so 2 comes before 10, not after it.
Sum and number statisticsAdd up a list of numbers and get the mean, median, min, max and standard deviation.
Sum numbersFind all numbers in text and add them together instantly.
Temperature converterConvert temperatures between Celsius, Fahrenheit and Kelvin, one value per line.
Time zone overlap findernewFind the hours when everyone across a list of time zones is in working hours.
Unit converternewConvert values between length, mass, volume, area, speed, pressure and energy units.
VAT calculatornewCalculate the net, VAT and gross amount for a whole list of prices at once.
Week number calculatornewGet the ISO 8601 week number for any date, or the dates spanning a given week.
Weighted average calculatornewCalculate a weighted average from a list of values and their weights.
Words to numbersTurn spelled-out English numbers in a text into digits, keeping everything else intact.

Numbers

Numbers have their own set of chores, and these tools handle the common ones: spell out an amount in words for a contract or invoice, convert Roman numerals in either direction, generate a numeric sequence with a chosen step, compute quick statistics — sum, average, median, min and max — over a pasted column of values, convert between bytes, KB, MB and GB, and validate a credit card number with the Luhn checksum.

Each tool replaces an awkward workaround. Writing amounts in words by hand invites the exact transposition errors the convention exists to catch; the converter gets it right every time. Number stats saves opening a spreadsheet just to sum a column from an email. The byte converter settles the eternal 1000-versus-1024 confusion by showing both interpretations explicitly.

The card validator deserves a special note: it checks the Luhn algorithm locally, in your browser, so a card number you test is never transmitted anywhere — unlike with online checkers that post the number to a server. It verifies the checksum only; it cannot and does not check whether an account exists.