Tukuk-OS🧰 Everyday Tools
Converters · calculators · checkers · generators — all computed on your device
The honest kind of useful. A hundred small tools that people actually search for — and that do their whole job inside your browser. Your text, your files, your dates, your passwords and your colours are processed on your own machine and never sent to us; there is no API to be down, no account, no download, and no tracking. The page works even after it has loaded on a plane.
In the toolbox
📐 Unit converter — eight categories with exact, definition-based factors (1 inch really is 2.54 cm); every unit in the category updates at once.
📅 Date & age calculator — counting days between deadlines, ages to the day, working days between dates, and the reliable days-until-birthday.
🎨 Colour & contrast checker — the official WCAG maths with pass/fail badges, and it suggests the nearest colour that does pass.
🔐 Password generator — uniform random picks from your browser’s cryptographic generator with real entropy numbers, not a smiley face.
✂️ Text toolkit — word & reading time counts, six case styles, URL and Base64 encode/decode, and SHA-256 hashes for file or text integrity.
❤️ BMI & calorie calculator — the health numbers that come from arithmetic: BMI bands, healthy weight range, and calorie needs from the published Mifflin-St Jeor equation.
🖼️ Image compressor — shrink photos and screenshots with quality and resize controls; your file is re-encoded on your own device and never uploaded.
📖 Dictionary & translator — word meanings and translation across dozens of human languages, plus ancient scripts and playful animal/alien/sound codes, all with spoken pronunciation.
🧮 Percentage calculator — the four questions people actually type: what is X% of Y, X is what percent of Y, percent change, and adding or subtracting a percentage — with the arithmetic shown.
🏦 Loan & compound interest calculator — monthly payment, total interest, the real savings from overpaying, and what regular saving grows into after compounding.
🔳 QR code generator — links, text and Wi-Fi credentials into a scannable code with L/M/Q/H error correction, drawn on a canvas and downloaded as a print-ready PNG.
📍 What is my IP? — your public address, the ISP and inferred city from a keyless database, and the browser fields any site can read, all explained instead of hidden.
⏱ Unix timestamp converter — epoch to date and back, seconds-versus-milliseconds auto-detection, ISO 8601, time zones and a live clock.
🎲 Random numbers & dice — unbiased integer ranges, d4–d100 rolls and a raffle-style list picker from the operating system’s cryptographic generator.
📄 PDF tools — merge, extract, delete, rotate and split pages; the file is opened and re-saved by your browser, so the document never reaches a server.
🧩 JSON formatter — format, minify and validate with the exact line and column of an error, keeping large numbers and key order intact.
🔑 Checksum & hash — MD5 through SHA-512 for text or a whole file, so a download can be checked against its published value without handing the file to anyone.
🔁 Base64 encoder — correct UTF-8 both ways, URL-safe output and a file turned into a data: URL, with the caveat that encoding is not encryption.
🌍 Time zone meeting planner — up to eight cities, every hour of the chosen day, with true UTC offsets and the best overlap named for you instead of counted by hand.
🆔 UUID generator — random v4 and time-ordered v7 in bulk, plus a decoder that reports the version, variant and any timestamp hiding inside an identifier.
⏰ Cron expression explainer — a schedule in plain English with its next ten runs on your clock, every field range-checked, and the day-of-month/day-of-week OR trap spelled out.
🔍 Regex tester — write a pattern, see live match highlighting with groups; a common-pattern library gets you started on email, URL and IPv4.
📊 CSV viewer & converter — paste delimited text, get a formatted table and clean JSON, with RFC 4180 quoting handled correctly.
🔀 Text diff — compare two blocks of text line-by-line or word-by-word; see additions and deletions highlighted instantly.
🔗 URL parser & encoder — break a URL into every component, or encode/decode query values side-by-side to catch the classic percent-encoding bug.
🔣 Character & Unicode reference — inspect code points, HTML entities, UTF-8 bytes and UTF-16 units for any character; a quick-reference table for typographic symbols.
🧭 Compass & bearing — a live on-screen compass off your phone’s magnetometer, with the great-circle bearing and distance to any world city; a desktop without a sensor falls back to a manual dial.
🔄 Image converter — convert between PNG, JPEG, WebP, BMP and ICO, and turn an SVG into a real picture at any size; the file is decoded and re-encoded by your own browser and never uploaded.
🖼️ Images to PDF — assemble photos, scans or screenshots into one document, A4 or Letter or sized page-per-image; JPEG and PNG files are embedded byte-for-byte, with no re-compression and no upload.
🔢 base converter — binary ⇄ hex ⇄ decimal and any base 2–36, exact for numbers far past what a calculator holds, with the digit-by-digit maths shown
🧬 text ↔ binary — type words, get their UTF-8 bytes in 01s (or hex/octal/decimal), and paste bytes back into text exactly
🧷 prime checker & factoriser — a proven (not "probably") primality answer for numbers up to 2⁶³ and the prime factorisation underneath any composite
🍕 fraction calculator — 1/3 + 1/6 answered as 1/2 with every step — common denominator, reduction by GCD, mixed-number and decimal forms
📈 statistics calculator — paste a column of numbers, get mean, median, mode, standard deviation, quartiles and IQR — with each formula named beside it
💼 salary converter — $25/hour vs $52,000/year, settled in one table — with the overtime rate and an honest "gross, before tax" label
🍽️ tip & bill split — bill, tip %, heads — out come the tip, the total and what each person pays, rounded up to avoid the odd-coin stand-off
🏷️ discount calculator — what does 30% off then another 20% coupon really cost — the final price, money saved, and the single equivalent percentage
⏳ countdown timer — any moment in the future or past, counted to the second and totalled in days and weeks, alive on the page without an app
🎓 grade calculator — current grade, final weight, target — out comes the score you need, or the honest impossibility plus the best case
🔣 html entities — make <script> safe to display, turn "©" into © or back, using the browser's own codec
🎫 jwt decoder — what is inside my token — every claim decoded, exp/iat shown as real dates, with the signature-never-verified warning in the copy, not the fine print
🏛️ roman numerals — MMXXVI for any year or chapter number, both directions, with the six subtractive pairs enforced instead of guessed
🔤 number to words — fill the cheque line right: 1,234,567.89 becomes "one million two hundred thirty-four thousand… five hundred sixty-seven dollars and 89 cents", exactly
⏲️ duration converter — turn 202600 seconds into "2 days, 8 hours, 16 minutes, 40 seconds" — and back — with the month/ambiguity traps named
🧾 check digit validator — test a card, IBAN, ISBN or barcode against its own check digit — the arithmetic shown, and nothing you type goes anywhere
🛒 unit price comparison — two packets, one truth: the cheaper-per-gram option, by how much, and what the other would have to cost to match
⛽ fuel economy calculator — 480 km on 30 litres: 6.25 L/100 km, 16 km/L, 37.6 US MPG — and the cost per 100 km at your pump price
😴 sleep-cycle calculator — alarm at 06:30? be asleep by 21:15, 22:45 or 00:15 — the cycle model, the maths shown, no medical claims
📝 lorem ipsum generator — the industry’s placeholder text, generated honestly: pseudo-Latin from the actual Cicero word bank, in as many paragraphs as your mockup needs
📐 aspect ratio calculator — the ratio behind your screenshot, simplified by Euclid’s algorithm, matched to the nearest standard, fitted into any box
📏 css unit converter — 24 px is 1.5 rem at a 16 px root — the whole conversion table, with the em footgun explained instead of fake-converted
🎲 dice probability — exact dice odds by convolution over every outcome — not a Monte Carlo guess — up to 10d20, with the full curve shown
⏬ download time calculator — 4.7 GB at 100 Mbps is 6 min 16 s, not 38 — the bits/bytes and decimal/binary traps both handled, plus a realistic row
🧮 combination calculator — choose or arrange: exact nCr, nPr and n! with the multiplicative steps, and the C(n,r)=C(n,n−r) symmetry doing the work
➗ gcd & lcm calculator — the paper-and-pencil maths shown line by line: Euclid's divisions, the lcm built from the gcd, and fraction-reducing as a bonus
🔺 triangle solver — 3-4-5 tells you it is right: every angle from the law of cosines, area from Heron, and a refusal to solve sides that cannot close
📖 readability checker — is your writing news-simple or journal-dense? the 1948 Flesch score plus grade level, counted word by word without uploading anything
🔥 calorie & tdee calculator — what you burn at rest, what you burn per day, and exactly which 250/500 kcal row moves the scale — Mifflin maths, stated with its error bars
💹 inflation calculator — 3% for 10 years turns 1,000 into 1,343.92 — the compounding printed year by year, plus how fast your money halves itself
🗝️ caesar & vigenère cipher — rotate, mirror or polybius-square the alphabet: four classic ciphers both directions, with the honest note that none of them survive a afternoon of cryptanalysis
🖌️ paint coverage calculator — buy the right number of tins: gross wall area, openings deducted, spread rate honoured, and the second coat nobody prices in
🥘 recipe scaler — paste the ingredient list, set servings from/to: every line rescaled to real spoon fractions, with the one baking rule that scales badly
🖨 print size calculator — does this file print poster-size? pixels divided by dpi, printed in inches and cm, with the viewing distance at which it still looks sharp
💡 electricity cost calculator — is the old fridge worth replacing? watts × hours × your tariff to a kWh figure and an annual cost, standby included
🏃 running pace calculator — a 25-minute 5K is 5:00/km — until it is not: even splits, and the Riegel-formula marathon prediction that admits the wall exists
🎨 design studio — make the social image yourself: templates, layered text/shapes/photos, drag-handle-rotate-snap, undo, autosave, PNG-JPG-WebP export — and your file never leaves the tab
💧 water target — a daily water goal built from body weight, exercise minutes and climate, shown as litres, glasses and an hourly drinking plan
🌱 compound interest — compound a principal plus regular savings, see the yearly table, the effective annual rate and how long money actually takes to double
🧾 tax add & remove — the two directions of tax maths (adding a rate, and removing it from an inclusive price) with the precise split each time
🫁 breathing pacer — a visual pacer for 5-5 coherent, box 4-4-4-4 and 4-7-8 breathing with phase labels and a round countdown
📡 morse code — type it or dot it — encode, decode, and hear SOS at the correct 1:3:7 unit timing, no radio required
🗣️ phonetic alphabet — the "can you repeat that over the phone" tool — spell it in NATO words, or paste a word chain back into letters
🗓️ week number — what week is it? ISO-8601 the correct way (not the +1 the spreadsheet got), day of year, and what dates a given week spans
📝 markdown to html — quick md → html with a deliberately small, fully predictable subset of CommonMark — safe by escaping first, not by filtering later
🔤 case converter — the copy-from-stackoverflow formatting tool: every dev naming style at once, with the acronym-aware split shown
📍 coordinate distance — two map pins in, straight-line-over-the-globe distance out — with the rhumb-line bearing and a map of why it is not the driving distance
🗓️ calendar grid — plan-a-month calendar with real week numbers, the right length of every month and leap years handled by the 4/100/400 rule
⌨️ typing speed test — measure your real typing speed the way every benchmark defines it, with per-keystroke feedback and an accuracy score
🎓 gpa calculator — credits-weighted GPA and CGPA from a pasted course list, with the per-course working and the catch-up sum to reach a target
👟 shoe size converter — centimetres to EU, UK and US shoe sizes and back, from the published formulas, with the ±half-size brand tolerance spelled out
📱 screen & ppi — two screens compared on the numbers that matter — physical width and height, PPI, and the area percentage the diagonal hides
🎵 metronome — a Web Audio click track from 40 to 208 BPM with accented downbeats and the classical tempo ranges beside every number
⏱️ stopwatch & laps — a centisecond stopwatch with lap splits and fastest/slowest detection, clocked from Date.now so throttling cannot drift it
🩸 blood type punnett — a 2×2 Punnett square of ABO genotypes returning children\u2019s phenotype odds and the classic inheritance surprises
🧬 dna translator — DNA to complement, reverse complement, mRNA and protein via the standard genetic code, with GC content
🕸️ subnet calculator — a CIDR breakdown — network, mask, wildcard, broadcast and usable host range of any IPv4 block, computed exactly
💓 hr zones — five Karvonen training zones from age and resting heart rate, with the better max-HR formulas beside the 220−age rule
☕ caffeine half-life — the half-life curve of caffeine after any dose, with the hour it drops below sleepy thresholds and a bedtime check
🌙 moon phase — the mean synodic cycle gives the Moon\u2019s age, illumination and phase name for any calendar date
✝️ easter date — Western and Orthodox Easter from the classical computus — golden number, epact and the full-moon-to-Sunday rule, for any year 1583-4099
📅 weekday finder — the weekday of any date, the years a date falls on a chosen weekday, and day-offset arithmetic that keeps the weekday
⏳ days between dates — days and business days between any two dates, in either counting convention, with weeks, months and the y-m-d form
🗄️ kb vs kib — any storage size in exact bytes with both the decimal and binary readings — the KB/KiB gap, and megabits versus megabytes
🔐 password strength — a password's entropy in bits with the common-password and keyboard-run penalties, and an honest offline-crack time
🔁 repeating decimal — any fraction expanded to its exact repeating decimal with the cycle length and the remainder proof, BigInt-exact
⌨️ keyboard test — a live keyboard test with key codes, pressed state and a completeness counter for checking every switch works
🍅 pomodoro timer — a pomodoro focus timer with work, short and long phases and a session tally, clocked from Date.now so throttling cannot drift it
📖 reading time — a reading-time estimator that counts words locally and prices them at the measured 238, 160 and 130 words-per-minute speeds
🏷️ ean-13 barcode — an EAN-13 barcode generator with the modulo-10 check digit, the first-digit parity encoding and a canvas drawing you can print at 2 px per module
✂️ slug generator — a URL slug maker with real accent folding, symbol spelling, separator collapsing and a word-boundary-safe length cut
Why browser-local, and why it matters to you
Most “free tool” sites ship your input to a server, paste eight ads around it and remember nothing about how the maths works. Here every answer comes from arithmetic your browser can verify: unit factors from international definitions, date counts from the Gregorian calendar itself, contrast ratios from the published WCAG formula, passwords from the operating system’s random source. That makes them private by construction — a password page that runs locally is not a promise, it is a fact you can check in your network tab.