Converters
Unit, date, number-base, colour and data-size conversions. The kind of thing you would otherwise open a search engine for — except the answer appears as you type and nothing is uploaded.
Unit ConverterInstantly convert length, mass, temperature, data and speed. Accurate, fast and easy to read.Timestamp ConverterConvert Unix timestamps to human dates (UTC, local, ISO) and back.Number Base ConverterConvert numbers between binary, octal, decimal and hexadecimal, live.Color ConverterPick a color and convert between HEX, RGB and HSL instantly.JSON ⇄ CSVConvert a JSON array to CSV and CSV back to JSON, with selectable delimiters, in your browser.Cron ParserParse a cron expression into a plain-language schedule and field breakdown, in your browser.Roman NumeralsConvert numbers to Roman numerals and back, instantly in your browser.Data Size ConverterConvert data sizes between bytes, KB, MB, GB and more, in both SI and IEC units.Percentage CalculatorCalculate percentages: X% of Y, what percent X is of Y, and percent increase or decrease.Date DifferenceFind the difference between two dates in years, months, weeks and days — and calculate age.Contrast CheckerCheck the WCAG contrast ratio between two colors and see AA/AAA pass or fail, in your browser.Aspect Ratio CalculatorCalculate aspect ratios and the missing width or height while keeping the proportion, in your browser.Timezone ConverterConvert a date and time between timezones around the world, using your browser and the IANA database.Number to WordsSpell out any number in English words (e.g. 1234 → one thousand two hundred thirty-four), in your browser.Text to BinaryConvert text to binary and back. See UTF-8 bytes as binary, decimal and hex, or decode 8-bit groups into text. Fast, free and fully private.CSS Unit ConverterConvert between px, rem, em, pt and % for any root font-size. Enter a value and every unit updates live, then copy any result with its unit.Business Days CalculatorCount the working days (Mon–Fri) between two dates, or add business days to a date, excluding weekends and your own holiday list — in your browser.Event CountdownLive countdown to any date and time, showing days, hours, minutes and seconds and updating every second — right in your browser.Time Duration CalculatorAdd or subtract durations in HH:MM:SS, and find the difference between two clock times. Get a normalized result plus total minutes and seconds.Week Number (ISO)Find the ISO-8601 week number, ISO year and weekday for any date, see the current week, and look up the Mon–Sun dates for a given year and week.Shoe Size ConverterConvert shoe sizes between US, UK, EU and JP (cm) for men and women — enter your size in one system and see the rest, with a full chart.Fuel Economy ConverterConvert fuel economy between US mpg, UK (imperial) mpg, L/100km and km/L — enter one and see all the others instantly, in your browser.JSON ⇄ YAMLConvert JSON to YAML and YAML to JSON in your browser — paste, switch direction, and copy. Nothing is uploaded.