Free Unit Converters
Convert between metric, imperial and US units in one step. Pick the units, type a number, and the result updates instantly, together with a reference table of common values.
Conversion factors come from the international definitions (for example, 1 inch is exactly 2.54 cm), so the results are exact wherever the definition is exact.
30 free tools · No sign-up · Works on phones and computers
Start here
Popular converters tools
- Unit ConverterConvert any common unit: length, weight, temperature, volume and more.
- Length ConverterMeters, feet, inches, centimeters, miles, kilometers and more.
- Weight ConverterKilograms, pounds, ounces, grams, stones and tons.
- Temperature ConverterCelsius, Fahrenheit and Kelvin, with the formulas shown.
- Cooking Unit ConverterCups, tablespoons, millilitres, grams and ounces — with ingredient densities.
All converters tools
Grouped by what they help you do.
30 tools
- Unit ConverterPopularConvert any common unit: length, weight, temperature, volume and more.
- Length ConverterPopularMeters, feet, inches, centimeters, miles, kilometers and more.
- Weight ConverterPopularKilograms, pounds, ounces, grams, stones and tons.
- Temperature ConverterPopularCelsius, Fahrenheit and Kelvin, with the formulas shown.
- Area ConverterSquare meters, square feet, acres, hectares and more.
- Volume ConverterLiters, gallons (US and UK), cups, milliliters and cubic units.
- Speed Converterkm/h, mph, meters per second, knots and feet per second.
- Data Size ConverterBytes, KB, MB, GB and TB — in both decimal and binary units.
- Pressure ConverterPSI, bar, pascals, atmospheres and mmHg.
- Energy ConverterJoules, calories, kilocalories, kWh and BTU.
- Time ConverterConvert between seconds, minutes, hours, days, weeks, months and years.
- Power ConverterWatts, kilowatts, horsepower, BTU/h and tons of refrigeration.
- Frequency ConverterHz, kHz, MHz, GHz, RPM and radians per second.
- Force ConverterNewtons, kilonewtons, pounds-force, kilograms-force and dynes.
- Torque ConverterNewton-metres, pound-feet, pound-inches and kgf·m.
- Density Converterkg/m³, g/cm³, g/mL, lb/ft³ and pounds per gallon.
- Angle ConverterDegrees, radians, gradians, arcminutes, arcseconds and turns.
- Fuel Economy ConverterMPG (US and UK), km/L and L/100 km — converted correctly both ways.
- Data Transfer Rate ConverterMbps to MB/s, Gbps, kB/s and more — internet speeds in bits and bytes.
- Cooking Unit ConverterPopularCups, tablespoons, millilitres, grams and ounces — with ingredient densities.
- Roman Numeral ConverterConvert numbers to Roman numerals and back, from 1 to 3,999.
- Number to Words ConverterWrite any number out in English words, including cheque format.
- Decimal to Fraction ConverterTurn any decimal — including repeating decimals — into a simplified fraction.
- Scientific Notation ConverterWrite numbers in scientific, E and engineering notation, with significant figures.
- Number FormatterFormat numbers with thousands separators for any country, round, or make them compact.
- Pixels to Print Size ConverterHow big an image prints at any DPI — or the pixels you need for a print size.
- Screen Size CalculatorWidth, height and pixel density of any screen from its diagonal and aspect ratio.
- Clothing Size ConverterUS, UK, EU, Italian and Japanese clothing sizes for women and men.
- Shoe Size ConverterUS, UK and EU shoe sizes and foot length for men and women.
- Paper Size ChartExact A, B, C and US paper sizes in mm, inches, points and pixels.
Good to know
US vs UK (imperial) units
Some units share a name but not a size. A US gallon is about 3.785 litres while a UK (imperial) gallon is about 4.546 litres. A US fluid ounce is slightly larger than a UK fluid ounce. The converters label these separately so you always pick the right one.
Converters tools: common questions
How precise are the conversions?
Results are calculated to full precision and rounded only for display. You can copy the full-precision result.
Can I convert temperatures?
Yes. The temperature converter handles Celsius, Fahrenheit, Kelvin and Rankine, which need formulas rather than a single multiplication factor.
Explore other categories
- 41 tools
Calculators
Percentages, algebra, statistics, geometry and everyday math.
- 22 tools
Finance
Loans, mortgages, interest, savings and salary in plain numbers.
- 42 tools
Text
Count words, change case, clean up and compare text.
- 61 tools
Developer
Format, validate, convert and encode code and data.
- 33 tools
Images
Compress, resize, crop and convert photos in your browser.
- 35 tools
PDF
Merge, split, rotate and convert PDF files.
- 15 tools
Audio
Trim, join, speed up and clean up audio, and record your voice.
- 11 tools
Files
Zip, unzip, compress, rename and inspect files.
- 9 tools
SEO
Meta tags, schema, robots.txt, sitemaps and SERP previews.
- 16 tools
Web
QR codes, URL tools, UTM links and browser info.
- 31 tools
Design
Colors, palettes, gradients, contrast and CSS helpers.
- 29 tools
Business
Invoices, receipts, margins, markup, VAT and ROI.
- 29 tools
Date & Time
Age, date differences, time zones, timers and clocks.
- 9 tools
Security
Strong passwords, passphrases, hashes and secure tokens.
- 8 tools
Health
BMI, calories, body fat, water intake and sleep.
- 52 tools
Education
Grades, GPA, physics, chemistry, engineering and biology.
- 15 tools
Everyday
Random pickers, dice, a notepad, typing test and more.
- 5 tools
Smart Text
Summarize, extract keywords, analyze tone and count tokens.