Unit Converter
Free online unit converter. Convert time, length, weight, temperature, and data size instantly.
How to Use
- Select a category: Time, Length, Weight, Temperature, or Data Size
- Enter a value in the input field
- Choose the source and target units
- The result updates instantly — click any row below to select it as the target unit
- Use the ⇄ button to swap the two units
Frequently Asked Questions
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How accurate are the conversions?
All conversions use standard international definitions. Results are accurate to 10 significant figures.
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Can I convert between metric and imperial units?
Yes. Length supports mm, cm, m, km as well as inch, foot, yard, and mile. Weight supports grams, kilograms alongside ounces and pounds.
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How is data size conversion calculated?
Data size uses binary prefixes: 1 KB = 1024 bytes, 1 MB = 1024 KB, and so on.
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Does this tool work offline?
Yes. All calculations happen in your browser with no server requests.
Why Unit Conversion Still Matters
Despite global efforts to standardize on the metric system, unit conversion remains a daily practical challenge. The United States, Liberia, and Myanmar still use the imperial system for everyday measurements. Scientific fields use SI units while engineering often mixes both. International trade, travel, cooking, construction, and software all require fluent unit conversion.
The Metric System (SI)
The International System of Units (SI) is the modern metric system used by science, medicine, and most of the world. It is a decimal system built on seven base units:
- Meter (m) — length
- Kilogram (kg) — mass
- Second (s) — time
- Ampere (A) — electric current
- Kelvin (K) — temperature
- Mole (mol) — amount of substance
- Candela (cd) — luminous intensity
All other units derive from these. The power of the metric system lies in its prefixes: kilo- (×1000), centi- (×0.01), milli- (×0.001), etc. make scaling trivial.
Imperial and US Customary Units
The imperial system evolved organically in Britain and was inherited by the United States, which later diverged slightly (the US gallon ≠ the imperial gallon, for example). Imperial units lack a consistent scaling factor — there are 12 inches in a foot, 3 feet in a yard, 1,760 yards in a mile. This makes mental arithmetic significantly harder.
Common conversions worth memorizing:
- 1 inch = 2.54 cm (exact, by definition)
- 1 mile = 1.609 km
- 1 pound = 0.4536 kg
- 1 US gallon = 3.785 liters
Temperature: A Special Case
Temperature conversion is non-linear, which makes it uniquely counterintuitive.
- Celsius to Fahrenheit:
°F = (°C × 9/5) + 32 - Fahrenheit to Celsius:
°C = (°F − 32) × 5/9 - Celsius to Kelvin:
K = °C + 273.15
Key reference points: water freezes at 0°C / 32°F, boils at 100°C / 212°F. Body temperature is 37°C / 98.6°F.
Data Size: Binary vs. Decimal Prefixes
Data size has a persistent ambiguity. Hard drive manufacturers use decimal prefixes (1 GB = 1,000,000,000 bytes) because it makes their products look larger. Operating systems historically used binary prefixes (1 GB = 1,073,741,824 bytes). The IEC introduced gibibyte (GiB), mebibyte (MiB) etc. to remove this ambiguity, but colloquial usage still conflates them.
This tool uses the binary definition (1 KB = 1024 bytes) consistent with how most operating systems report file and memory sizes.