Free Online Unit Converter
Convert between units of length, weight, temperature, volume, area, speed, data storage, and time instantly. This free online unit converter covers the most commonly searched conversions across eight categories. Convert kilometers to miles, pounds to kilograms, Celsius to Fahrenheit, liters to gallons, acres to hectares, and hundreds more — with results updating in real time as you type. Each conversion shows the exact formula so you can verify the math or use it in your own calculations. The converter handles both metric and imperial units, including less common ones like stones, nautical knots, and fluid ounces. A swap button lets you reverse the conversion direction instantly. The tool also covers digital data units (bytes to gigabytes using the standard 1024 base) and time units from milliseconds to years. All calculations run in your browser with no server calls. Whether you are cooking with a foreign recipe, planning a road trip abroad, or converting data sizes for a technical spec, this tool gives you accurate answers immediately.
Frequently Asked Questions
Multiply the Celsius temperature by 9/5 (or 1.8) and add 32. For example, 25°C × 1.8 + 32 = 77°F. To convert the other way, subtract 32 from the Fahrenheit temperature and multiply by 5/9. This tool handles the conversion automatically — just select Temperature, choose your units, and type the value.
One mile equals exactly 1.609344 kilometers. Conversely, one kilometer equals approximately 0.621371 miles. A quick mental approximation: multiply km by 0.6 to get a rough miles estimate, or multiply miles by 1.6 to get rough km.
Metric units (meters, grams, liters) use base-10 prefixes — kilo means 1000, centi means 1/100. Imperial units (feet, pounds, gallons) use irregular conversion factors (12 inches in a foot, 16 ounces in a pound). Most countries use metric; the US, Myanmar, and Liberia still primarily use imperial for everyday measurements.
Both conventions exist. In computing (RAM, file systems), 1 KB = 1024 bytes (binary). In storage marketing (hard drives, SSDs), 1 KB = 1000 bytes (decimal). The IEC standard uses KiB (kibibyte) for 1024 and KB for 1000, but most people still say KB for both. This tool uses the 1024 (binary) convention, which matches how operating systems report file sizes.
All conversions use exact mathematical conversion factors (e.g., 1 inch = exactly 25.4 mm, 1 pound = exactly 0.45359237 kg). Results are displayed to 6 significant digits, which is more than sufficient for any practical purpose. Temperature conversions use the exact formulas, not approximations.
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