Everyday Tools

This category collects the small tools people reach for several times a month: percentages and fractions, dates and time spans, word and character counts, password and UUID generators, QR codes and barcodes, encoders and converters for developers, and a few just-for-fun generators. They share one design rule — everything runs locally in your browser. The text you paste, the password you generate and the dates you enter are processed on your own device and are not sent to a server.

Several of these tools have more going on under the surface than their size suggests, and we document it. The password generator and dice roller draw from the browser's cryptographically secure random source and use rejection sampling to avoid a subtle bias; the random-number tool uses a Fisher–Yates shuffle when you ask for unique values; the barcode generator computes the check digit for retail formats; the URL encoder follows the same percent-encoding rules your browser uses; and the time and date calculators handle overnight shifts, month lengths and leap years.

Entertainment tools such as the love calculator are labeled clearly as entertainment. They are deterministic and fun, not predictive, and we say so on the page. If a tool is for serious use — hashing, encoding, formatting JSON, counting characters against a platform limit — the page explains exactly what it does and its limits so you can rely on it appropriately.

Thirty-three tools in six groups

A category this wide is easier to use once you know its groups. For dates and time there are the Age Calculator, the Date Difference Calculator, the Time Duration Calculator and the Countdown Timer, which doubles as a Pomodoro focus timer. For numbers and math there are the Percentage Calculator, Fraction Calculator, Scientific Calculator, GPA Calculator, Number Base Converter and Roman Numeral Converter. For randomness there are the Random Number Generator, Dice Roller, Coin Flip, Random Wheel, Password Generator and UUID Generator, plus the lighter name and word pickers: the Random Name Generator, Fantasy Name Generator, Username Generator and Random Word Generator.

Writers and editors get the Word Counter, Character Counter, Case Converter, Lorem Ipsum Generator and Text to Speech. Developers get the JSON Formatter, URL Encoder and Decoder, Hash Generator and Binary Translator. Makers of printed and shareable things get the QR Code Generator, Barcode Generator and Color Palette Generator. The Love Calculator sits on its own as pure entertainment.

The sections below walk through what the less obvious tools really do, because the details decide whether a tool fits a job. Where an everyday question has a matching guide on this site, such as how to calculate percentages, GPA, age and date gaps, or how to create a strong password, the guide covers the method in prose and the tool does the arithmetic.

Randomness: which generators are strong and which are for fun

Not every random tool here uses the same source, and the difference matters. The Password Generator, UUID Generator, Dice Roller, Coin Flip and Random Wheel all draw from the cryptographically secure generator built into your browser. The Dice Roller takes a 32-bit random value and uses rejection sampling, discarding values above the largest multiple of the die's sides, so d6 and d20 faces are exactly equally likely. The Coin Flip reads a byte and sends 128 of the 256 possible values to heads and 128 to tails, an exact split. The Random Wheel picks a segment from that same secure source, so no entry has an advantage because of where it sits.

The Random Number Generator and the name and word pickers use the standard Math.random function, which is perfectly good for games, giveaways among friends and writing prompts but is not designed for security. The Random Number Generator also shows how uniqueness is handled: when duplicates are off, it shuffles the whole range and takes the first values, so a request for more unique numbers than the range holds returns an error instead of a short list. The name, word and username pickers choose independently with no repeat protection, so a long list can contain the same entry twice.

Strength figures are worth knowing. The Password Generator's full set has 88 characters, so a 16-character password has about 1.3 times 10 to the 31st possible combinations. A version 4 UUID carries 122 random bits. These numbers describe the generator, not your habits, so store passwords in a manager and use a different one for every account.

Dates, durations and countdowns, with examples

The date tools handle month lengths and leap years so you do not have to. The Age Calculator returns years, months and days, total days lived and days to the next birthday, and it accepts a comparison date, so you can ask how old someone was at a past event. The Date Difference Calculator reports total days from a straight subtraction and, separately, a years, months and days breakdown found by borrowing between calendar units. Because the dates are read at midnight local time, only the calendar date matters, and entering the same date twice returns zero.

The Time Duration Calculator is built for timesheets. A shift from 9:15 to 17:30 with a 30 minute unpaid break is 7 hours 45 minutes, which is 7.75 in decimal hours, the format payroll systems usually want. If the end time is earlier than the start, it assumes one midnight crossing and adds 24 hours, so 22:00 to 06:30 is 8 hours 30 minutes. It cannot represent a shift longer than 24 hours, and a break longer than the shift gives zero rather than a negative number.

The Countdown Timer is the short-interval tool in this group. You pick a preset from 1 to 60 minutes, it counts down once per second, and it sounds a tone at zero. In Pomodoro mode it alternates 25 minutes of focus with 5 minutes of break. Its completed-session counter is kept in the page only, so a refresh resets it, and the beep is generated by your browser rather than played from a file.

Percentages, fractions, GPA and number systems

Percent change is measured from the starting value, which makes it asymmetric. A drop from 80 to 40 is 50 percent, but a rise from 40 back to 80 is 100 percent. A decrease can never exceed 100 percent, while an increase has no ceiling: 10 to 100 is a 900 percent increase. The Percentage Calculator handles three questions, the percentage of a number, what percent one number is of another, and percent change, and it reports an error when the base is zero.

The GPA Calculator weights each grade by credit hours on the standard 4.0 scale. Take a 4-credit A, a 3-credit B plus, a 3-credit A minus and a 1-credit B. The quality points are 16, 9.9, 11.1 and 3, a total of 40 over 11 credits, so the GPA is about 3.64. Change the 4-credit grade to an F and the GPA falls to about 2.18, which shows why heavy courses dominate. The tool uses the unweighted scale and gives an A plus the same 4.0 as an A.

The Fraction Calculator reduces answers to lowest terms and shows a fraction, mixed number and decimal; enter a negative mixed number with the minus sign on the whole part. The Number Base Converter shows binary, octal, decimal and hexadecimal together, so decimal 42 is 101010 in binary, 52 in octal and 2A in hex. The Roman Numeral Converter covers 1 through 3999, so 1994 is MCMXCIV. The Scientific Calculator follows standard order of operations, accepts degrees or radians, and trims results to 12 significant digits to hide floating-point noise.

Text, code and developer utilities: what to expect

The Word Counter estimates reading time at 200 words per minute and speaking time at about 130. The Character Counter adds progress against common limits, and it counts sentences by punctuation, so abbreviations containing periods inflate the total. The Case Converter capitalizes every word in Title Case with no small-word exceptions, which means an acronym such as NASA becomes Nasa, and an apostrophe splits a word in programmer styles. The Lorem Ipsum Generator builds filler from a fixed Latin-style word list, and Text to Speech uses the voices your device already provides.

For developers, the JSON Formatter uses the browser's strict parser, so comments and trailing commas are flagged as errors. The URL Encoder and Decoder offers a Component mode that encodes reserved characters and a Full URL mode that leaves the structure intact. The Hash Generator computes SHA-1, SHA-256, SHA-384 and SHA-512 digests of text, giving 40, 64, 96 and 128 hexadecimal characters. The Binary Translator converts text to UTF-8 bytes, so a character outside basic ASCII can take two to four 8-bit groups.

For codes and color, the QR Code Generator encodes whatever text you type at error-correction level M, which tolerates roughly 15 percent damage, and longer text makes a denser code. The Barcode Generator supports CODE128, CODE39, EAN-13, UPC-A and ITF-14 and works out the check digit for the retail formats. The Color Palette Generator picks five random hues in balanced saturation and lightness, and you can lock the ones you like.