The Only Unit Converter You'll Ever Need
Simple, fast, and scientific-grade precision. Convert anything from nanometres to light years in seconds.
How it works
Every conversion goes through a carefully defined base unit with Decimal.js arithmetic—so homework, recipes, lab notes, and engineering estimates stay stable instead of drifting with binary floating-point math. Pick a category, choose two units, and read the formulas, tables, and FAQs on each page.
Temperature
Convert Celsius, Fahrenheit, Kelvin and more.
Volume
Convert Cubic Nanometre, Cubic Micrometre, Picolitre and more.
Length
Convert Planck Length, Yoctometre, Zeptometre and more.
Area
Convert Barn, Square Nanometre, Square Micrometre and more.
Weight
Convert Kilogram, Gram, Milligram and more.
Speed
Convert Metre per second, Kilometre per hour, Mile per hour and more.
Time
Convert Second, Millisecond, Microsecond and more.
Learn with our guides
Original explainers on metric vs imperial, temperature scales, SI prefixes, cooking conversions, and more.
Metric vs Imperial: Which System Should You Use?
A practical comparison of metric and imperial units for length, volume, and area—when each system wins and how to convert between them confidently.
How Unit Conversion Works: Factors, Bases, and Dimensional Analysis
Learn the mechanics behind unit conversion—base units, conversion factors, dimensional analysis, and why chaining conversions carefully keeps answers exact.
Why Floating-Point Converters Fail (and How Decimal Math Fixes It)
Understand why binary floating-point creates weird conversion residuals, when those errors matter, and how decimal or rational arithmetic keeps unit converters trustworthy.
Celsius, Fahrenheit, and Kelvin Explained
Clear formulas, fixed points, and practical advice for converting between Celsius, Fahrenheit, and Kelvin without mixing offsets and scale factors.
Built for everyday and scientific use
Whether you are converting body height for a form, room area for flooring, oven temperature for a recipe, or pool volume for chemicals, Units Converters gives you a clear result plus context—unit descriptions, worked examples, and guides that explain the systems behind the numbers.
Common conversions
- Centimetre to Inch (International)
- Inch (International) to Centimetre
- Inch (International) to Foot (International)
- Millimetre to Inch (International)
- Inch (International) to Millimetre
- Meter to Foot (International)
- Foot (International) to Meter
- Kilometre to Mile (International)
- Mile (International) to Kilometre
- Centimetre to Foot (International)
- Foot (International) to Centimetre
- Meter to Yard (International)
- Yard (International) to Meter
- Meter to Kilometre
- Foot (International) to Inch (International)
- Yard (International) to Foot (International)
- Nanometre to Meter
- Light Year to Kilometre
- Celsius to Fahrenheit
- Fahrenheit to Celsius
- Celsius to Kelvin
- Kelvin to Celsius
- Fahrenheit to Kelvin
- Kelvin to Fahrenheit
- Square Metre to Square Foot
- Square Foot to Square Metre
- Acre to Hectare
- Hectare to Acre
- Square Kilometre to Square Mile
- Square Mile to Square Kilometre
- Square Inch to Square Centimetre
- Square Centimetre to Square Inch
- Square Metre to Hectare
- Acre to Square Metre
- Litre to Cubic Metre
- Cubic Metre to Litre
- Millimetre to Litre
- Litre to Millimetre
- Cup to Millimetre
- Millimetre to Cup
- Cubic Foot to Litre
- Litre to Cubic Foot
- Tablespoon (Metric) to Teaspoon (Metric)
- Teaspoon (Metric) to Tablespoon (Metric)
- Hectolitre to Litre
- Litre to Hectolitre
- Kilogram to Pound (Avoirdupois)
- Pound (Avoirdupois) to Kilogram
- Gram to Ounce (Avoirdupois)
- Ounce (Avoirdupois) to Gram
- Kilogram to Stone
- Stone to Kilogram
- Tonne (Metric) to Pound (Avoirdupois)
- Pound (Avoirdupois) to Tonne (Metric)
- Gram to Kilogram
- Kilogram to Gram
- Milligram to Gram
- Gram to Milligram
- Kilometre per hour to Mile per hour
- Mile per hour to Kilometre per hour
- Metre per second to Kilometre per hour
- Kilometre per hour to Metre per second
- Mile per hour to Foot per second
- Foot per second to Mile per hour
- Knot to Kilometre per hour
- Kilometre per hour to Knot
- Metre per second to Mile per hour
- Mile per hour to Metre per second
- Minute to Second
- Second to Minute
- Hour to Minute
- Minute to Hour
- Day to Hour
- Hour to Day
- Week to Day
- Day to Week
- Year (Julian) to Day
- Day to Year (Julian)
- Hour to Second
- Second to Hour
Precision Unit Converter: Metric, Imperial & Scientific
Quickly convert between hundreds of units across Length, Temperature, Area, and Volume. Whether you are a student, engineer, or hobbyist, our tool provides high-precision results for everything from everyday measurements to advanced scientific data.
Comprehensive Categories
- Length: Nanometres to Light Years and Planck Length.
- Temperature: Celsius, Fahrenheit, Kelvin, and Newton.
- Area: Square Meters, Acres, Hectares, and Barns.
- Volume: Litres, Cubic Inches, Gallons, and Millilitres.
Why Use Our Converter?
- Ultimate Precision: Powered by Decimal.js for zero rounding errors.
- Scientific Grade: Includes rare units like Bohr, Ångström, and Parsecs.
- Instant Results: Real-time conversion as you type.
- Mobile Friendly: Optimized for use on any device.
Our free online converter is the fastest way to switch between metric and imperial systems. Save time on complex math and get reliable conversions for school, lab work, or construction projects.