Free Online Unit Converters
Convert between metric, imperial and US customary units with the exact factors defined by the international standards — not rounded approximations. Each converter shows the formula and a reference table.
All Converters (59 Available)
Unit Converter
Convert length, weight, temperature, volume, speed and more.
Length Converter
Convert metres, feet, inches, miles, kilometres and more.
Weight Converter
Convert kilograms, pounds, ounces, stones and tonnes.
Temperature Converter
Convert Celsius, Fahrenheit, Kelvin, Rankine and Réaumur.
Area Converter
Convert square metres, feet, acres, hectares and more.
Volume Converter
Convert litres, gallons, cups, millilitres and cubic units.
Speed Converter
Convert km/h, mph, m/s, knots and Mach.
Data Storage Converter
Convert bytes, KB, MB, GB, TB and their binary equivalents.
Time Unit Converter
Convert seconds, minutes, hours, days, weeks and years.
Pressure Converter
Convert pascals, bar, psi, atmospheres and mmHg.
Energy Converter
Convert joules, calories, kWh, BTU and electronvolts.
Power Converter
Convert watts, kilowatts, horsepower and BTU per hour.
Angle Converter
Convert degrees, radians, gradians and turns.
Fuel Economy Converter
Convert MPG, km/L and L/100km correctly.
CM to Inches Converter
Convert centimetres to inches, with a fraction option.
Inches to CM Converter
Convert inches to centimetres, including fractional inches.
MM to Inches Converter
Convert millimetres to inches for engineering and DIY.
Feet to Meters Converter
Convert feet and inches to metres exactly.
Meters to Feet Converter
Convert metres to feet and inches.
KG to Pounds Converter
Convert kilograms to pounds and stones.
Pounds to KG Converter
Convert pounds and stones to kilograms.
Celsius to Fahrenheit Converter
Convert °C to °F with the formula shown.
Fahrenheit to Celsius Converter
Convert °F to °C with the formula shown.
KM to Miles Converter
Convert kilometres to miles for distance and speed.
Miles to KM Converter
Convert miles to kilometres for distance and speed.
JSON to CSV Converter
Turn a JSON array into a spreadsheet-ready CSV.
CSV to JSON Converter
Convert CSV or spreadsheet data into clean JSON.
JSON to YAML Converter
Convert JSON into readable YAML for configuration files.
YAML to JSON Converter
Convert YAML configuration into JSON.
Base64 Encoder
Encode text to Base64, with UTF-8 and URL-safe support.
Base64 Decoder
Decode Base64 back to readable text, standard or URL-safe.
URL Encoder
Percent-encode text for safe use in URLs and query strings.
URL Decoder
Decode percent-encoded URLs back into readable text.
Colour Converter
Convert between HEX, RGB, HSL, HSV and CMYK.
HEX to RGB Converter
Convert a hex colour code to RGB values.
RGB to HEX Converter
Convert RGB values to a hex colour code.
RGB to HSL Converter
Convert RGB values to hue, saturation and lightness.
HSL to RGB Converter
Convert hue, saturation and lightness to RGB and hex.
Number Base Converter
Convert numbers between binary, octal, decimal, hex and any base.
Binary to Decimal Converter
Convert binary numbers to decimal with the working shown.
Decimal to Binary Converter
Convert decimal numbers to binary with the division steps.
Hex to Decimal Converter
Convert hexadecimal numbers to decimal.
Decimal to Hex Converter
Convert decimal numbers to hexadecimal.
Image Converter
Convert between JPG, PNG and WebP in any direction.
JPG to PNG Converter
Convert JPG photos to lossless PNG files.
PNG to JPG Converter
Convert PNG images to smaller JPG files.
JPG to WebP Converter
Convert JPG to WebP and cut file size by around 30%.
PNG to WebP Converter
Convert PNG to WebP, keeping transparency at a fraction of the size.
WebP to JPG Converter
Convert WebP images to widely compatible JPG files.
WebP to PNG Converter
Convert WebP to PNG with transparency preserved.
GIF to PNG Converter
Extract a GIF frame as a lossless PNG image.
PDF to Image
Convert PDF pages to PNG or JPG at a resolution you choose.
PDF to JPG
Turn every PDF page into a JPG image.
Image to PDF
Combine images into a single PDF with proper page sizing.
JPG to PDF
Convert JPG photos into a PDF document.
PNG to PDF
Convert PNG images into a PDF, keeping quality intact.
Text to Binary Converter
Convert text into its binary representation, byte by byte.
Binary to Text Converter
Decode binary back into readable text.
Text to ASCII Converter
Convert between text and character codes in any base.
About Converters
All length, mass and volume conversions here are anchored to the international yard and pound agreement of 1959, which defines one inch as exactly 25.4 millimetres and one pound as exactly 0.45359237 kilograms. Everything else derives from those exact values.
Where a unit is ambiguous — the US gallon versus the imperial gallon, the US fluid ounce versus the imperial one, the short ton versus the metric tonne — both are listed separately rather than silently picking one.
The dedicated single-pair converters exist because that is how people search and because each one can carry the formula, worked examples and a quick-reference table for that specific conversion.
Converters FAQs
How precise are these conversions?
Conversions use exact internationally defined factors where they exist and full double-precision arithmetic throughout. You choose how many decimal places to display; rounding happens only at that final step.
Which gallon does the volume converter use?
Both. US liquid gallons and imperial (UK) gallons are separate units in the list, as are US and imperial fluid ounces, pints and quarts, because they differ by around 20%.
Why do temperature conversions work differently?
Temperature scales have different zero points, so they need an offset as well as a ratio. Celsius to Fahrenheit is (C × 9/5) + 32, not a single multiplication. Kelvin and Rankine are absolute scales with no negative values.
Can I convert currencies here?
No. Exchange rates change by the second, and publishing a stale rate would be worse than publishing none. These converters only cover units with fixed, defined relationships.