Unit Converter
Convert length, weight, temperature, speed, and data. Select a category, enter a value, and see all conversions instantly — no calculator needed.
Result
0.6214mi
1 km = 0.6214 mi
All conversions
Why use our online Unit Converter?
Convert between units of measurement instantly without installing an app. Supports length, weight, temperature, volume, area, speed, and more — all calculated locally in your browser.
How to use Unit Converter
- 1Select a category
Choose the unit category you need — Length, Weight, Temperature, Area, Volume, Speed, Data, or Time.
- 2Enter a value
Type the number you want to convert into the input field. The conversion updates instantly as you type.
- 3Choose the source and target units
Select the unit you're converting from and the unit you want the result in from the dropdown menus.
- 4Read or copy the result
The converted value appears immediately. Click to copy it for use in other applications.
Why metric and imperial coexist — and why it matters
The metric system (SI units) is the international scientific standard, used in almost every country and all scientific disciplines. The imperial system (inches, pounds, Fahrenheit, gallons) is primarily used in the United States for everyday life, with the UK and a few other countries using a hybrid.
The practical consequence is that unit confusion causes real errors. In 1999, NASA lost the $125 million Mars Climate Orbiter because one team provided force values in pound-force seconds while another expected newton seconds. The spacecraft entered Mars's atmosphere at the wrong angle and was destroyed. Unit conversion is not a trivial exercise.
For everyday use, the most common conversions are temperature (Celsius to Fahrenheit: multiply by 9/5, then add 32), weight (kilograms to pounds: multiply by 2.20462), and distance (kilometres to miles: multiply by 0.621371). These are worth memorizing for travel and international recipe adaptation.
Temperature conversion — understanding the three scales
Three temperature scales are in common use. Celsius (°C) is based on water freezing at 0° and boiling at 100° at standard pressure. It is the everyday scale used in most countries and in science.
Fahrenheit (°F) is the US everyday scale. Water freezes at 32°F and boils at 212°F. To convert: °F = (°C × 9/5) + 32. Human body temperature is 37°C or 98.6°F. Room temperature is roughly 20–22°C or 68–72°F.
Kelvin (K) is the scientific absolute scale where 0 K is absolute zero — the lowest possible temperature, at which atomic motion theoretically stops. There are no negative Kelvin values. To convert from Celsius: K = °C + 273.15. Kelvin is used in physics, chemistry, thermodynamics, and astrophysics. Note: Kelvin values are expressed without a degree symbol (300 K, not 300°K).
Digital storage units — bits, bytes, and why 1 KB is not always 1,000 bytes
Storage units have two competing definitions that cause consistent confusion. In the traditional binary system, 1 kilobyte = 1,024 bytes (2¹⁰), 1 megabyte = 1,048,576 bytes (2²⁰), and so on. This is how operating systems historically reported file sizes and how RAM is measured.
The decimal system defines 1 kilobyte = 1,000 bytes (10³), 1 megabyte = 1,000,000 bytes, and so on. Hard drive manufacturers use the decimal definition, which is why a 1 TB drive shows as approximately 931 GB in Windows (which uses the binary definition).
To resolve this ambiguity, the IEC introduced prefixes in 1998: kibibyte (KiB) = 1,024 bytes, mebibyte (MiB) = 1,048,576 bytes, gibibyte (GiB) = 1,073,741,824 bytes. These are exact and unambiguous. This converter uses the IEC binary definitions for digital storage conversions.
Length and distance — practical conversions for everyday use
Length is the most common category for unit conversion. The key metric-to-imperial relationships worth remembering: 1 inch = 2.54 cm (exact, by definition since 1959). 1 foot = 30.48 cm. 1 meter = 3.281 feet = 39.37 inches. 1 kilometer = 0.6214 miles. 1 mile = 1.609 km.
For travel, the quick approximation for kilometres to miles is to multiply by 0.6 (or divide by 1.6). A 100 km/h speed limit is roughly 62 mph. A 5-km run is roughly 3.1 miles. A marathon (42.195 km) is 26.22 miles.
Clothing and screen sizes use inches in much of the world even in otherwise metric countries: screen diagonals (a 15.6-inch laptop), waist measurements (32-inch jeans), and television sizes are almost universally quoted in inches. Paper sizes switch between systems: the US uses Letter (8.5 × 11 inches) while most of the world uses A4 (210 × 297 mm). A4 is slightly taller and narrower than Letter — this matters when printing documents intended for an international audience.
Weight, volume, and cooking conversions
The weight conversions most frequently needed: 1 kg = 2.205 lbs. 1 lb = 453.6 grams. 1 stone (UK body weight measure) = 14 lbs = 6.35 kg. For cooking, 1 ounce = 28.35 grams; most kitchen recipes scale accurately at 30 g per ounce.
Volume is where the systems diverge most confusingly. The US gallon (3.785 L) differs from the UK imperial gallon (4.546 L) — a difference that matters when importing fuel economy figures. The US cup (240 mL) is a uniquely American unit with no metric equivalent; UK recipes use millilitres or weight for liquids. 1 US tablespoon = 14.79 mL; 1 teaspoon = 4.93 mL.
Cooking conversions between volume and weight depend entirely on ingredient density. "1 cup of flour" is approximately 120–130 g, but "1 cup of water" is exactly 240 g, and "1 cup of butter" is 227 g. This is why serious baking recipes specify ingredients by weight (grams) rather than volume — it eliminates the compressibility problem of dry ingredients like flour and gives consistent results regardless of how tightly the ingredient is packed.
Frequently Asked Questions
Which unit categories does the converter support?
- The tool covers Length, Weight/Mass, Temperature, Area, Volume, Speed, Digital Storage, and Time — covering the most common everyday and scientific conversion needs.
How accurate are the conversions?
- Conversions use precise conversion factors and are accurate to at least 10 significant figures, which is more than sufficient for everyday and professional use.
Does it support imperial and metric units?
- Yes. Both metric (SI) and imperial/US customary units are supported across all categories.
Is a network connection required?
- No. All conversions are computed locally in your browser. The tool works fully offline after the page has loaded.
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