Kongzi Business Web ยท Free Online Toolbox
A curated set of 2226 utilities for JSON, encoding, hashing, images, units, dates and SEO. Everything computes locally in your browser for privacy, with no install and a smooth mobile experience.
Random picks
40 tools, reshuffled on every refresh
CSS Beautify & Minifysynonym and antonym Reference TablekW to horsepowerMaple Syrup Cup to Gram ConverterHow Many in a Hectare? Hectare Referencechain to kmkilometres per hour to knothectopascal to kPakgf/cmยฒ to bartonne of oil equivalent to BTUdecade to yearkHz to rpmlux to photL/s to L/minPaยทs to lb/(ftยทs)pap_quire to cnt_reamnewton to pound-forcenewton to gram-forceg/s to lb/hmg/L to mmol/LChicago Time ConverterPlaceholder Image GeneratorSolid Colour Image MakerContrast CheckerCSS Stripe PatternBank Card ValidatorXGA PPI and Sizebaby clothing size Reference Tableimposition layout CalculatorMolar Mass CalculatorModulo CalculatorSphere CalculatorPotential Energy CalculatorPhoton Energy CalculatorInflation CalculatorSolar Financing Monthly Payment CalculatorLuxury Tax CalculatorROI and Payback PeriodPregnancy BMI Calculatorweight-based dosing Calculator
Tool categories
Pick a category to browse every tool
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Developer Tools
JSON, code formatting, regex testing and developer helpers
69 tools ยท Open
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Encryption & Hashing
MD5, Base64, AES, URL encoding and hash digests
37 tools ยท Open
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Text Utilities
Counting, replacing, dedupe, case and symbol handling
45 tools ยท Open
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Unit Converters
Length, area, weight, temperature and data storage
1318 tools ยท Open
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Date & Time
Timestamps, date intervals, countdowns and calendars
51 tools ยท Open
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Image Tools
Compress, convert, resize and pick colors from images
48 tools ยท Open
๐จ
Color & Design
Palettes, gradients, color conversion and CSS generators
32 tools ยท Open
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Everyday Life
Health, finance, documents and everyday lookups
123 tools ยท Open
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Webmaster & SEO
Encoding checks, robots, TDK and site diagnostics
21 tools ยท Open
โฆ
QR & Barcode
QR generation, styling, barcodes and scenario encoders
11 tools ยท Open
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Media & Documents
Media info, audio trimming, image to PDF, recording
19 tools ยท Open
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PDF Tools
Merge, split, extract, delete, rotate, watermark, number, encrypt PDFs
16 tools ยท Open
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Study & Reference
Chemistry, math drills, reference tables and quick facts
23 tools ยท Open
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Math & Geometry
Equations, fractions, logs, trigonometry, geometry, matrices and sequences
69 tools ยท Open
โ
Physics & Chemistry
Velocity, force, energy, Ohm law, gas laws, molarity and equation balancing
58 tools ยท Open
๐ฐ
Finance & Money
Loans, compound interest, ROI, retirement savings, inflation and real returns
80 tools ยท Open
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Statistics
Distributions, hypothesis tests, confidence intervals, regression and sample size
24 tools ยท Open
๐ฉบ
Health & Medical
BMR/TDEE, body fat, target heart rate, drug dosing and clinical scores
67 tools ยท Open
๐ฎ
Divination & Folklore
BaZi, Zi Wei, Qi Men, feng shui, astrology, tarot, numerology, runes and coffee reading โ entertainment only
50 tools ยท Open
๐ง
Engineering
Concrete, paint, wire sizing, voltage drop, beam loads and pipe flow
65 tools ยท Open
Popular tools
The utilities people reach for most
{}JSON Formatter & ValidatorBeautify, minify and validate JSON with precise error locations.โฒJSON Minify & EscapeTurn JSON into a single line or an escaped string literal.โJS Beautify & MinifyBeautify or minify JavaScript with indentation and comment control..*Regex TesterHighlight regex matches live with groups and positions.โText DiffCompare two texts line by line with clear markers.#MD5 Hash GeneratorTurn text into a 32 or 16 character MD5 digest.โSHA Hash GeneratorGenerate SHA-1, SHA-256 and SHA-512 digests in one go.โทBase64 Encoder & DecoderEncode text to Base64 or decode it back.01Number Base ConverterConvert between binary, octal, decimal and hex live.๐Password GeneratorCreate strong random passwords with custom rules.โWord & Character CounterLive counts of characters, words, lines and paragraphs.โFind & ReplaceBatch replace text with regex and case options.
Developer Tools
JSON, code formatting, regex testing and developer helpers
{}JSON Formatter & ValidatorBeautify, minify and validate JSON with precise error locations.โฒJSON Minify & EscapeTurn JSON into a single line or an escaped string literal.โงJSON to Entity ClassConvert a JSON shape into Java entity classes, nested objects included.โนJSON DiffCompare two JSON documents key by key.โJS Beautify & MinifyBeautify or minify JavaScript with indentation and comment control.โฃCSS Beautify & MinifyBeautify or compress CSS with comments removed.โHTML Beautify & MinifyReindent HTML into a readable tree or compress it.โSQL FormatterReindent SQL and uppercase keywords for readability.โจโฉXML FormatterIndent or compress XML to inspect configs and payloads..*Regex TesterHighlight regex matches live with groups and positions.โธRegex Code GeneratorGenerate Java, JS, Python, PHP and Go snippets from a regex.โฑCron Expression GeneratorBuild cron expressions visually with a readable explanation.
Encryption & Hashing
MD5, Base64, AES, URL encoding and hash digests
#MD5 Hash GeneratorTurn text into a 32 or 16 character MD5 digest.โSHA Hash GeneratorGenerate SHA-1, SHA-256 and SHA-512 digests in one go.โทBase64 Encoder & DecoderEncode text to Base64 or decode it back.%URL Encoder & DecoderPercent-encode text or decode it back.01Number Base ConverterConvert between binary, octal, decimal and hex live.โฌกHex to Text ConverterConvert between text and hexadecimal.AzASCII Code ConverterConvert between characters and ASCII codes in three bases.โธUTF-8 EncoderInspect UTF-8 bytes and Unicode escapes for your text.u4Unicode Escape ConverterConvert between text, Unicode escapes and HTML entities.๐Password GeneratorCreate strong random passwords with custom rules.๐Text Encrypt & DecryptEncrypt text with a passphrase or restore it.โฟJWT DecoderDecode JWT header and payload with expiry check.
Text Utilities
Counting, replacing, dedupe, case and symbol handling
โWord & Character CounterLive counts of characters, words, lines and paragraphs.โFind & ReplaceBatch replace text with regex and case options.โText DeduplicatorRemove duplicate lines and count them.โ Add Line NumbersAdd incremental numbers to every line.AaCase ConverterFive modes for converting letter case.โทFull-width & Half-width ConverterConvert between full-width and half-width characters.โSpecial SymbolsBrowse symbols by category and copy with one click.โLine SorterSort lines by alphabet, length or numeric value.โText ReverserReverse text overall, per line or by word order.โซWhitespace CleanerRemove blank lines, trim lines and collapse spaces.โธLine ExtractorExtract lines by number range.PYChinese to PinyinConvert Chinese to pinyin, with initials and tones.
Unit Converters
Length, area, weight, temperature and data storage
๐Length ConverterConvert between 10 length units live.โWeight ConverterConvert common mass units live.โฆArea ConverterConvert area units including mu and acres.๐งชVolume ConverterConvert common volume units live.๐กTemperature ConverterConvert Celsius, Fahrenheit and Kelvin.๐Speed ConverterConvert speed units including knots and Mach.๐พData Storage ConverterConvert decimal and binary storage units.๐ฌPressure ConverterConvert common pressure units live.๐Angle ConverterConvert degrees, radians, arcminutes and arcseconds.โณTime Unit ConverterConvert time units from milliseconds to years.โกPower ConverterConvert watts, kilowatts and both horsepower types.โIPv4 Subnet CalculatorCompute network, broadcast and usable host range.
Date & Time
Timestamps, date intervals, countdowns and calendars
โฑUnix Timestamp ConverterConvert timestamps and dates in both directions.๐
Date CalculatorFind the gap between dates or offset a date.โณCountdown TimerShow live time remaining until a target date.โนDate IntervalShow the gap in years, months, days and workdays.๐Age CalculatorGet exact age, zodiac, constellation and birthday countdown.๐Beijing Time NowShow Beijing and local time to the second.๐Lunar Calendar ConverterConvert between Gregorian and lunar dates.๐พ24 Solar TermsList all 24 solar terms with dates and meanings.๐World ClockSee the time in several cities with offsets.โฒStopwatchStart, pause, lap and reset to 0.01 seconds.๐Festival CalendarTraditional and modern observances in one list.โTime DifferenceFind the duration between two times across midnight.
Image Tools
Compress, convert, resize and pick colors from images
๐Image CompressorCompress images by quality and size with a size comparison.๐Image Format ConverterConvert between JPG, PNG and WebP.โคขImage ResizerResize images by pixels or percentage.โนImage InfoInspect image dimensions, size and format.๐งImage WatermarkAdd a customizable text watermark.๐จImage FiltersAdjust brightness, contrast, saturation and blur live.๐Image Color PickerPick colours from an image as HEX and RGB.โฆImage Grid SplitterSplit an image into grid tiles for download.๐ผBase64 to ImageTurn a Base64 string back into an image file.๐Image to PDFCombine multiple images into one PDF.โ Rounded Corners & ShadowApply rounded corners and shadow, export PNG.โIdenticon GeneratorGenerate deterministic pixel avatars from text.
Color & Design
Palettes, gradients, color conversion and CSS generators
๐จColor Palette GeneratorGenerate harmonious palettes from a base colour.๐CSS Gradient GeneratorBuild and copy CSS gradient code visually.โColor ConverterConvert HEX, RGB, HSL, HSV and CMYK.โColor Shade GeneratorGenerate a light to dark colour ramp.โชCSS Box Shadow GeneratorGenerate box-shadow code visually.โCSS Border Radius GeneratorIndependent corner radii with copyable CSS.โฉWeb Safe Colors216 web safe colours with click to copy.โจGradient CollectionCurated gradients with copyable CSS.๐Image Palette ExtractorExtract dominant colours from an image.โContrast CheckerCheck WCAG contrast between text and background.โณCSS Animation GeneratorGenerate common CSS animations with copyable code.โฒCSS Triangle GeneratorGenerate CSS triangles in any direction.
Everyday Life
Health, finance, documents and everyday lookups
โBMI CalculatorGet BMI and health range from height and weight.๐ Mortgage CalculatorCompare monthly payments and total interest.๐Car Loan CalculatorCompute car payments from price, down payment and rate.๐งพIncome Tax CalculatorEstimate monthly tax and take-home pay.โฝFuel Consumption CalculatorCompute fuel consumption and cost per kilometre.๐คฐDue Date CalculatorEstimate due date and gestational week.๐Chinese ZodiacLook up zodiac animals by birth year.โจStar Sign FinderFind your star sign from a birth date.๐ฒRandom PickerDraw random winners from a list.๐What to EatPick a random dish to end indecision.๐กMorse Code TranslatorTranslate between text and Morse code.โ
ซRoman Numeral ConverterConvert numbers and Roman numerals.
Webmaster & SEO
Encoding checks, robots, TDK and site diagnostics
๐คrobots.txt GeneratorGenerate a robots.txt file visually.๐ทMeta Tag GeneratorGenerate a complete set of head meta tags.๐Title & Description CheckerCheck title and description lengths.๐Keyword Density AnalyzerMeasure keyword frequency and density.๐บSitemap GeneratorTurn URLs into a sitemap.xml file.๐HTTP Status CodesLook up HTTP status codes by class.๐URL CheckerCheck URL formatting and get advice.๐งญDomain Info GuideExplain domain structure and DNS records.๐Nofollow Link BuilderGenerate links with rel attributes.AaFont Size ConverterConvert between px, rem, em and pt.๐Title Uniqueness CheckerDetect duplicate and similar titles.๐งฉSchema Markup GeneratorGenerate JSON-LD structured data markup.
QR & Barcode
QR generation, styling, barcodes and scenario encoders
โฆQR Code GeneratorTurn text or a URL into a QR code.โQR Code StylerAdd rounded dots, gradients and a centre logo.๐URL to QR CodeTurn a URL into a scannable QR code.๐ถWiFi QR CodeCreate a scan-to-connect Wi-Fi QR code.๐คvCard QR CodeCreate a scan-to-save contact QR code.โฅBarcode GeneratorGenerate Code 128, Code 39 and EAN-13 barcodes.๐QR Code ReaderRead QR content from an image.โงBulk QR GeneratorGenerate many QR codes from a line list.๐ISBN & Barcode ValidatorCheck a barcode check digit.โฆQR Code CapacityEstimate the QR version, module count and minimum print size from length, mode and error correction.โฆQR Module SizeModule size and print dimension from QR version and the intended scan distance.
Media & Documents
Media info, audio trimming, image to PDF, recording
๐ฌMedia Info ViewerInspect media duration, resolution and format.โAudio TrimmerTrim audio by time range and export WAV.๐Voice RecorderRecord from your microphone and export WAV.๐ธVideo Frame CaptureCapture a video frame and export it as an image.๐Images to PDFCombine images into a single PDF.๐ผPDF to ImagesRender PDF pages to PNG images.๐ฅScreen RecorderRecord your screen and save a video.๐ตAudio File InspectorInspect an audio file's parameters.๐ฌSRT Subtitle RetimerFix subtitle timing.๐ฌVideo Bitrate and SizeEstimate the bitrate for a resolution and frame rate, then the file size for a given duration.๐ผRecording CapacityEstimate recording time from card capacity and bitrate across several resolutions.๐Frame Rate and Shutter AngleShutter speed from frame rate and shutter angle, with common angle references.
PDF Tools
Merge, split, extract, delete, rotate, watermark, number, encrypt PDFs
๐Merge PDFCombine multiple PDFs into one file.โSplit PDFSplit a PDF into several files.๐Extract PDF PagesPull out just the pages you need.๐Delete PDF PagesDrop the pages you do not need.๐Rotate PDFTurn PDF pages to the right orientation.๐Reorder PDF PagesPut PDF pages in your own order.#Add Page Numbers to PDFNumber the pages of a PDF automatically.๐งWatermark PDFStamp a watermark across PDF pages.๐Protect PDF with PasswordSet an open password on a PDF.๐PDF Unlock NotesLearn what password removal is possible.๐Compress PDFMake a PDF smaller by rebuilding it.๐ทPDF Metadata ViewerSee which details a PDF carries.
Study & Reference
Chemistry, math drills, reference tables and quick facts
โPeriodic TableLook up all 118 elements with key data.โMath Worksheet GeneratorGenerate arithmetic practice sets.โMultiplication TableGenerate a printable times table.๐ฏChinese Dynasties TimelineMajor dynasties in chronological order.๐Unit Conversion TutorShow conversion factors and steps.๐Vocabulary FlashcardsFlip through vocabulary cards.๐งฎMental Math DrillTimed drills with instant scoring.๐Classical Poetry QuotesSearch classical lines by keyword.๐Chinese Idiom DictionarySearch idioms with pinyin and meaning.โผChinese Character RadicalsLook up radicals and stroke counts.โChinese NumeralsConvert numbers to Chinese numerals.โMolar Mass CalculatorCompute molar mass from a chemical formula.
Math & Geometry
Equations, fractions, logs, trigonometry, geometry, matrices and sequences
โSquare Root CalculatorSquare, cube and n-th roots.ยฝFraction CalculatorFraction arithmetic and reduction.๏ผ
Percentage CalculatorAll four percentage questions in one go.ใLogarithm CalculatorLogarithms in any base.xโฟExponent CalculatorPowers with any base and exponent.๐ฌScientific Notation ConverterPlain numbers โ scientific notation.รทGCD & LCM CalculatorGCD and LCM of several integers.๐ขPrime FactorizationPrime factors, primality test and divisors.๐ฅยฒQuadratic Equation SolverSolve quadratics with full working.โSystem of Equations SolverSolve two-variable linear systems.๐Mean Median Mode CalculatorMean, median, mode and spread.ฯStandard Deviation CalculatorSample and population variance and SD.
Physics & Chemistry
Velocity, force, energy, Ohm law, gas laws, molarity and equation balancing
โถSpeed Distance Time CalculatorSpeed, time and distance.โAcceleration CalculatorAcceleration and uniform motion.โฐForce CalculatorForce, mass and acceleration.โกWork & Energy CalculatorKinetic and potential energy.ฮฉOhm's Law CalculatorVoltage, current, resistance, power.P VIdeal Gas Law CalculatorThe ideal gas equation PV = nRT.โMolar Mass CalculatorMolar mass from a formula.๐งชMolarity & Dilution CalculatorMolarity and dilution.ฯDensity CalculatorDensity, mass and volume.โฌPressure CalculatorPressure and unit conversion.โฟWavelength & Frequency CalculatorWavelength, frequency and photon energy.โBuoyancy CalculatorBuoyancy and floating.
Finance & Money
Loans, compound interest, ROI, retirement savings, inflation and real returns
๐ฆLoan Payment CalculatorMonthly payments and total interest.๐Compound Interest CalculatorCompound growth and effective yield.๐นROI CalculatorROI and annualised return.๐ดRetirement Savings CalculatorRetirement target and monthly saving.๐Inflation CalculatorInflation, prices and purchasing power.๐ฏSavings Goal CalculatorMonthly saving needed for a goal.๐ฆMortgage Monthly Payment CalculatorWork out the monthly payment, total interest and total repayment for a mortgage, with a first-year schedule.๐ฆCar Loan Monthly Payment CalculatorWork out the monthly payment, total interest and total repayment for a car loan, with a first-year schedule.๐ฆStudent Loan Monthly Payment CalculatorWork out the monthly payment, total interest and total repayment for a student loan, with a first-year schedule.๐ฆPersonal Loan Monthly Payment CalculatorWork out the monthly payment, total interest and total repayment for a personal loan, with a first-year schedule.๐ฆBusiness Loan Monthly Payment CalculatorWork out the monthly payment, total interest and total repayment for a business loan, with a first-year schedule.๐ฆCredit Card Installment Monthly Payment CalculatorWork out the monthly payment, total interest and total repayment for a credit card installment, with a first-year schedule.
Statistics
Distributions, hypothesis tests, confidence intervals, regression and sample size
๐Normal Distribution CalculatorNormal probabilities and Z scores.๐Confidence Interval CalculatorConfidence intervals for a mean.๐ฒSample Size CalculatorSurvey sample size and margin.๐งZ-Score CalculatorZ scores, percentiles and critical values.๐T-Test CalculatorOne- and two-sample t tests.๐Correlation & RegressionCorrelation and regression.๐One-Sample t-Test CalculatorTest whether a sample mean differs from a hypothesised value, reporting t, df and the critical-value verdict.๐Two-Sample t-Test CalculatorCompare the means of two independent samples with the difference, Welch standard error and t.๐Chi-Square Test CalculatorEnter the four counts of a 2ร2 table to get chi-square, the verdict and Cramรฉr V.๐Pearson Correlation CalculatorPearson r, coefficient of determination and regression slope from two series.๐Simple Linear Regression CalculatorFit a least-squares line to two series, reporting slope, intercept, Rยฒ and a prediction.๐Mean Confidence Interval CalculatorConfidence interval and margin of error for a mean using the large-sample approximation.
Health & Medical
BMR/TDEE, body fat, target heart rate, drug dosing and clinical scores
๐ฅBMR & TDEE CalculatorBMR and daily calorie needs.๐Body Fat CalculatorBody fat from circumference.โคTarget Heart Rate CalculatorTraining heart-rate zones.๐Drug Dosage CalculatorWeight-based dosing and infusion rates.โBMI & Metabolic AssessmentBMI, waist ratio and risk grading.โAdult BMI CalculatorEnter height and weight to get adult bmi, the category range and the weight change needed to reach a normal BMI.โChild BMI CalculatorEnter height and weight to get child bmi, the category range and the weight change needed to reach a normal BMI.โTeen BMI CalculatorEnter height and weight to get teen bmi, the category range and the weight change needed to reach a normal BMI.โAthlete BMI CalculatorEnter height and weight to get athlete bmi, the category range and the weight change needed to reach a normal BMI.โSenior BMI CalculatorEnter height and weight to get senior bmi, the category range and the weight change needed to reach a normal BMI.โPregnancy BMI CalculatorEnter height and weight to get pregnancy bmi, the category range and the weight change needed to reach a normal BMI.โคMax Heart Rate CalculatorCompute max heart rate from age and resting heart rate, with both Karvonen and percentage-of-max zones.
Divination & Folklore
BaZi, Zi Wei, Qi Men, feng shui, astrology, tarot, numerology, runes and coffee reading โ entertainment only
๐ฎBaZi Four Pillars ChartFour pillars and five-element balance from your birth time.๐ฎBaZi Five Elements AnalysisElement balance and favourable directions.๐ฎBaZi Luck PillarsEight luck pillars with a starting age.๐ฎZi Wei Dou Shu ChartLife palace, bureau and fourteen main stars.๐ฎZi Wei Twelve PalacesTwelve palaces with main stars.๐ฎQi Men Dun Jia ChartBureau, gates and stars on the nine palaces.๐ฎQi Men Eight GatesThe eight gates and their readings.๐ฎFeng Shui CompassAngle to bagua and twenty-four mountains.๐ฎEight Houses Kua CalculatorKua number, group and directions.๐ฎWestern Birth ChartSun, moon, rising signs and houses.๐ฎZodiac CompatibilityCompatibility score for two signs.๐ฎTarot Card DrawDraw cards and read their meanings.
Engineering
Concrete, paint, wire sizing, voltage drop, beam loads and pipe flow
๐งฑConcrete CalculatorConcrete volume and materials.๐จPaint Coverage CalculatorPaint needed for your walls.๐Wire Size CalculatorWire gauge, ampacity and voltage drop.โกVoltage Drop CalculatorVoltage drop and line loss.๐Beam Load CalculatorBeam moment, shear and deflection.๐Pipe Flow CalculatorPipe flow, velocity and regime.โTorque CalculatorTorque, power and speed.๐จPaint QuantityPaint volume and can count from room perimeter, ceiling height, openings and coats.โฆTile QuantityTiles and boxes needed from area, tile size, waste factor and pack quantity.๐ชตFlooring QuantityBoxes and planks needed from room size, plank spec and waste factor.๐งปWallpaper RollsRolls needed from wall area, roll spec and pattern-repeat waste.๐งฑConcrete Mix MaterialsCement, sand, gravel and water from pour volume and volumetric mix, converted to bags.
Why choose Kongzi Business Web
Focused on useful, clean and fast utilities
Your data stays local
Every calculation runs on your device. Nothing you type is uploaded anywhere.
No install, no signup
Open the page and start working. No downloads, accounts or fees.
Mobile and tablet ready
A mobile-first responsive layout with comfortable touch targets.
One-click copy
Each tool offers copy and download actions so results reach your workflow fast.
14 languages
Chinese, English, Hindi, Spanish, Arabic, French, Bengali, Portuguese, Indonesian, Urdu, Russian, German, Japanese and Korean.
Always growing
New utilities are added by category, with speed and accuracy tuned first.
Frequently asked questions
Every tool is free with no usage limits and no account required.
No. The logic runs locally in your browser, so input never leaves your device.
Yes. The whole site is mobile-first, so phones, tablets and desktops all work smoothly.
The site ships in 14 languages: Chinese, English, Hindi, Spanish, Arabic, French, Bengali, Portuguese, Indonesian, Urdu, Russian, German, Japanese and Korean.
Current versions of all major modern browsers on desktop and mobile.