Unit Converter
Convert length, weight, temperature, and more
Unit Converter tool
Common Conversions
- • 1 inch = 2.54 cm
- • 1 km = 0.621 miles
- • 1 foot = 0.3048 meters
Unit Converter: key facts
- What it does
- Convert length, weight, temperature, and more
- Category
- Converters
- Cost
- Free, with no account, sign-up, or install.
- Your data
- Runs entirely in your browser — the files and text you enter are never uploaded to a server.
- Last reviewed
- . Report an incorrect result.
Understanding the Unit Converter
Converting between measurement systems is a constant friction point—metric to imperial for cooking, Celsius to Fahrenheit for weather, megabytes to gigabytes for storage. The Unit Converter handles conversions across length, weight, temperature, area, volume, speed, time, data storage, and more in a single interface.
Students check homework answers, engineers convert between metric and imperial for international projects, cooks adjust recipes from different measurement systems, and everyday users make quick conversions without memorizing formulas. Each category uses precise conversion factors for accuracy.
Because conversions run entirely in your browser using JavaScript, you can convert values without any data leaving your device. The tool supports bidirectional conversion—swap the from/to units instantly to reverse the calculation without re-entering values.
Getting a result
- Select the unit category you want to convert from the tabs or dropdown: length, weight, temperature, area, volume, speed, time, or data storage.
- Enter the value you want to convert in the input field.
- Select the original unit from the "From" dropdown and the target unit from the "To" dropdown.
- View the converted result instantly—no need to click a calculate button as conversion happens in real-time.
- Click the swap button between the unit dropdowns to reverse the conversion direction without re-entering your value.
Conversion through a base unit
Each category defines one base unit and a factor for every other unit relative to it — metres for length, kilograms for mass, and so on. A conversion multiplies into the base and divides out, which means adding a new unit requires one number rather than a factor against every existing unit.
Temperature is handled separately, because it is the one category where conversion is not a simple ratio. Fahrenheit and Celsius have different zero points as well as different degree sizes, so the transformation needs an offset and cannot be expressed as a single multiplier.
Reference examples are shown per category, which are worth more than they look: knowing that a kilogram is about 2.2 pounds lets you sanity-check any result at a glance.
- 1 kg is 2.205 lb, and 1 oz is 28.35 g.
- 1 gallon is 3.785 litres — the US gallon; the imperial gallon is about 4.546 litres.
- Length, mass, volume, area, and time all convert by ratio; temperature does not.
Reasons to use it here
- All conversions happen locally in your browser using JavaScript—no data is sent to any server, and the tool works offline once the page has loaded.
- Supports multiple unit categories in one tool rather than requiring separate converters for length, weight, temperature, and other measurements.
- Uses precise mathematical formulas and standard conversion factors, providing accurate results to multiple decimal places for scientific and engineering applications.
- Real-time conversion updates as you type or change units, and the swap button lets you instantly reverse conversions without re-entering values.
The ambiguities that cause real errors
Several unit names mean different things in different places, and this is where conversions go wrong. The US and imperial gallons differ by about 20%, as do their pints and fluid ounces. A US ton is 2,000 pounds, an imperial ton 2,240, and a metric tonne 1,000 kilograms. A billion once meant a million million in British usage. None of these is a rounding difference.
Mass and weight are also distinct quantities routinely conflated. A kilogram is mass; a newton or a pound-force is weight, which depends on local gravity. Everyday use treats pounds and kilograms as interchangeable because gravity is near-constant on Earth's surface, but the distinction is real and matters in physics and engineering.
Unit errors have destroyed spacecraft — the Mars Climate Orbiter was lost in 1999 to a pound-force-seconds against newton-seconds mismatch between two systems. The professional habit is to carry units through every calculation rather than converting at the end, so that a dimensional inconsistency shows up as an obviously wrong unit rather than a plausible wrong number.
Frequently Asked Questions
What unit categories are supported?
The unit converter supports length (meters, feet, miles, etc.), weight (kilograms, pounds, ounces, etc.), temperature (Celsius, Fahrenheit, Kelvin), area, volume, speed, time, data storage, and more. New categories are added based on user feedback.
How accurate are the conversions?
Conversions use precise mathematical formulas and standard conversion factors defined by international standards. Results are accurate to multiple decimal places, making the tool suitable for scientific, engineering, and everyday use.
Can I convert multiple values at once?
Yes, you can convert as many values as needed. Simply enter a value and select the units—the conversion happens instantly. Change the value or units for additional conversions without refreshing the page.
Is this tool free to use?
Absolutely. The unit converter is completely free with no limitations, subscriptions, or hidden fees. Use it as often as you need for personal, educational, or commercial purposes.
Does it work offline?
Yes, once the page has loaded, all conversion logic runs in your browser using JavaScript. You can use the tool without an internet connection, making it reliable for field work or areas with poor connectivity.
