Herramientas online para el día a día

Small tools for everyday questions

Some questions come up every day: how old is someone exactly, how many days until a deadline, what is 15% of a price, how many words are in this essay, what time it is in Tokyo, heads or tails. These tools answer them in a second, on any device, without an app or an account.

• Calculators: the age calculator gives an exact age in years, months and days and counts down to the next birthday; the percentage calculator handles percent of a number, percentage change and percentage difference, and shows the formula. The date calculator counts the days, weeks, months and business days between two dates and adds or subtracts days, months or years; the scientific calculator handles trigonometry, logarithms, powers and factorials with a safe expression parser; and the GPA calculator works out semester and cumulative GPA on the US 4.0 scale, weighted or unweighted (see how GPA is calculated).
• Unit converters: the cm to inches converter also gives feet and inches for heights, the kg to lbs converter adds stones and pounds, and the Celsius to Fahrenheit converter works both ways and includes kelvin and oven temperatures. Each page has a conversion chart, the exact formula and a mental shortcut; the guide to metric and imperial conversions puts them side by side. The Roman numerals converter turns numbers, years and dates into Roman numerals and back, explains why a numeral is invalid and has a 1 to 100 chart; the guide how to read Roman numerals covers the rules. The Morse code translator converts text to Morse and back and plays it as sound or light at any speed (see the Morse code alphabet guide).
• Text: the word counter counts words, characters, sentences and paragraphs and estimates reading and speaking time as you type, which helps with essays, social posts and meta descriptions. The word unscrambler finds every English word you can make from a set of letters, with blanks and filters; text to speech reads any text aloud with your device's voices and highlights each word; and image to text pulls the words out of a photo or screenshot in your browser.
• Generators: the QR code generator turns links, Wi-Fi details, contacts and text into QR codes you can download as PNG or SVG; the barcode generator draws Code 128, EAN-13, UPC-A, EAN-8, Code 39 and ITF-14 barcodes with the check digit worked out (which barcode type to use); the random number generator picks fair numbers for draws, games and sampling; flip a coin tosses one or up to 100 fair coins with a running tally and streaks; and the yes or no wheel spins for yes, no or maybe, with best of 3 and openly weighted odds.
• Time: the online stopwatch records laps, and the online timer counts down with an alarm and includes a Pomodoro mode for focused work. The time zone converter converts a time between cities and helps plan meetings across zones, and the world clock shows the current time in cities around the world.
• Music: play a virtual keyboard with the online piano, which has easy songs to learn; tune a guitar, bass, ukulele or violin with your microphone using the guitar tuner (see how to tune a guitar); and keep time with the online metronome, which schedules every click on the audio clock and has tap tempo, time signatures and subdivisions.

For groups and classes, the spin the wheel name picker and the Team Quiz are in our team & classroom tools.

Guías

• Cómo saber si un texto es de IA y por qué fallan los detectores: Cómo saber si un texto está escrito por IA: los patrones que lo delatan, cómo funcionan los detectores, su fiabilidad y cómo revisar sin acusar en falso.
• Alucinaciones de la IA: qué son y cómo verificar a ChatGPT: Por qué ChatGPT, Gemini y Claude inventan datos, citas falsas y enlaces rotos, y cómo verificar paso a paso cualquier respuesta de IA antes de usarla.
• How to Spot AI-Generated Images: Metadata, C2PA and Visual Clues: Check whether a photo is AI-generated: Content Credentials (C2PA), IPTC AI labels, EXIF data, error level analysis, reverse image search and the visual tells.
• ¿Qué cuenta como plagio? Paráfrasis y citas: Guía clara sobre el plagio: copia, paráfrasis y patchwriting, autoplagio, texto escrito con IA, cómo citar bien y cómo comprobar un texto.
• Metric to Imperial: cm to Inches, kg to Pounds and °C to °F: Convert cm to inches, kg to pounds and stones, and Celsius to Fahrenheit: exact formulas, quick mental shortcuts, worked examples and handy tables.
• How to Read Roman Numerals (Chart and Rules): How Roman numerals work: the seven symbols, the adding and subtractive rules, how to read and write years, a 1 to 100 chart and why IIII appears on clocks.

Todas las guías

Preguntas frecuentes

Are these tools free?

Yes. All everyday tools are free, need no account and work on phones, tablets and computers.

Is what I type sent to a server?

No. The calculators, converters, word counter, word unscrambler, text to speech, image to text, generators, coin flip, yes or no wheel, time zone tools, piano, guitar tuner, metronome, stopwatch and timer all run in your browser. The guitar tuner listens to your microphone only after you press Start and never records or uploads the sound.

Is the yes or no wheel random?

Yes. Each spin draws the answer with your browser's cryptographically secure random number generator before the wheel turns. With equal weights, yes and no each have a 50% chance; if you set weights, the page shows the real odds.

Is the online coin flip fair?

Yes. Each flip uses your browser's cryptographically secure random number generator, so heads and tails each have exactly a 50% chance and earlier flips never influence the next one.

Can I put the barcodes I make on products sold in shops?

The generator draws any valid barcode, but EAN and UPC numbers for retail products must be licensed from GS1 (or your retailer's own scheme); a made-up number may clash with someone else's product. Code 128 and Code 39 are fine for your own labels, assets and inventory.

How exact are the unit conversions?

Exact to the shown decimals: an inch is defined as exactly 2.54 cm and a pound as exactly 0.45359237 kg, and °F = °C × 9/5 + 32. Results are rounded only for display.

Do the QR codes expire?

No. The QR codes are static: the link or text is stored in the code itself, so they keep working as long as the destination does.

Do the stopwatch and timer keep running in a background tab?

Yes. They measure elapsed time from your device's clock, so switching tabs does not slow them down; the timer alarm plays when time is up.