Small tools that do one thing.
Some useful, some not. Every one of them runs entirely in your browser. No accounts, no uploads, no server doing the work. View source if you like.
Money
2 toolsTime
5 tools- How Many Days Old Am I Your age in days, weeks and whole months, the weekday you were born on, and the dates the round numbers land on.
- Days Since Sign It has been this many days since whatever you like, with a full-screen mode for the wall.
- Unix Timestamp Converter A timestamp into a date and back, in seconds, milliseconds, microseconds or nanoseconds, UTC and local.
- As Long Ago As A date is as far from today as some earlier one was from it, and then as far again.
- Asymptotic Stopwatch Runs at true speed, then slows so it approaches your target time without reaching it.
Units
6 tools- Absurd Unit Converter Measurements restated in blue whales, boulders, eagles and swimming pools.
- Dog and Cat Years An animal's age in human years by the size table, the epigenetic clock, and the seven-times rule that is wrong.
- Indian Land Area Converter Bigha, kanal, marla, guntha, cent and gaj in square metres and feet, with the state convention it used printed underneath.
- Ohm's Law Calculator Any two of volts, amps, ohms and watts give the other two, with the power checked three ways on the page.
- Resistor Colour Code Bands into a resistance and back again, with the tolerance range and the preferred-value series.
- Decibel Converter dBm, dBW, watts, dBi, dBd and EIRP, keeping absolute powers and ratios apart.
Science
4 tools- Molar Mass Calculator A chemical formula into a molar mass, with the percent composition and the molecules in a weighed sample.
- Half-Life Calculator Radioactive decay: what is left after a time, how long to fall to a fraction, and the activity of a sample.
- Dew Point and Condensation Risk Three published formulas side by side, and how cold a surface has to be before it runs with water or grows mould.
- Great-Circle Distance The distance and bearing between two coordinates, on a sphere and on the WGS-84 ellipsoid, with the difference shown.
Maths
2 toolsDeveloper
13 tools- Hex and RGB Converter A colour in hex, rgb(), hsl(), HSB and CMYK, either direction, with its contrast ratios.
- Number Base Converter Binary, octal, decimal, hex and every base up to 36, exactly, with the two's complement view.
- URL Encoder and Decoder Percent-encoding in the four conventions that disagree, and a URL taken apart into its pieces.
- Subnet Calculator An IPv4 address and a prefix into the network, broadcast, host range and wildcard, with /31 handled properly.
- IEEE 754 Float Inspector The bits, and the exact decimal value a float really holds — every digit of it.
- Invisible and Confusable Characters Why two identical-looking strings compare unequal: zero-width spaces, bidi controls and Cyrillic lookalikes, located and named.
- JWT Decoder Read a token's header and claims without pasting it into someone else's server.
- CRC Calculator 104 named variants, any parameters you like, and the reverse question: which variant produced this CRC.
- Cron Expression Explainer Plain English, plus the next ten times it actually fires.
- Regex Tester Live match highlighting, capture groups and a replacement preview.
- Text Diff Compare two pasted blobs line by line, with the unchanged parts folded away.
- Unicode Text Mangler Sponge case, small caps, fullwidth, upside down and zalgo, with the code points and the byte count.
- SVG Path Optimizer Shortens a d attribute, then samples both curves to prove the shape did not move.
Media
6 tools- Aspect Ratio Calculator Resize at a fixed ratio or reduce a size to one, with the rounding, the even sizes and the letterbox bars all stated.
- Image Format Converter PNG, JPEG and WebP in any direction, with the output size shown as you drag the quality slider.
- EXIF Viewer and Stripper Shows what a photo knows about where it was taken, and removes it without recompressing.
- SMPTE Timecode Calculator Timecode, frames and real elapsed time, with drop-frame done properly and impossible timecodes refused.
- Video to GIF A few seconds of a video as an animated GIF, which then reads itself back to prove it decodes.
- Favicon Set Generator One square image in, the whole set out as a zip, with the manifest and the link block.
Chance
3 tools- Decision Ball Twenty answers, one drawn fairly, with the odds and the whole list printed on the page.
- Infinite Monkey Theorem How long a room of monkeys would take to type a given phrase, with every digit of the answer printed.
- Dice Roller Any dice notation, rolled with an unbiased generator, with the exact odds of the total printed beside it.