Unit Converter
Convert between metric and imperial units of length, weight, and volume instantly — no sign-up, no uploads, everything runs right in your browser. Need to convert temperature instead? Head over to the Temperature Converter. Scaling a recipe with cups, tablespoons, or teaspoons? The Cooking Unit Converter handles those kitchen-specific measurements. Converting money instead of measurements? Try the Currency Converter.
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About This Converter
Most of the world uses the metric system (meters, grams, liters), built on powers of ten so converting between units is just a matter of moving a decimal point. The United States, however, still relies heavily on the imperial / US customary system (feet, pounds, gallons) for everyday measurements, even though science, medicine, and most manufacturing in the US use metric units internally. This tool bridges the gap, letting you convert instantly between both systems for length, weight/mass, and volume.
How to Use
- Choose a category — Length, Weight & Mass, or Volume — using the tabs at the top of the calculator.
- Enter the number you want to convert in the Value field.
- Select the unit you're converting From and the unit you're converting To.
- The result updates automatically as you type or change units — no button required.
- Use the Swap button to quickly reverse the From and To units.
Common Conversions
Length
| Conversion | Result |
|---|---|
| 1 mile | 1.60934 km |
| 1 inch | 2.54 cm |
| 1 foot | 0.3048 m |
Weight & Mass
| Conversion | Result |
|---|---|
| 1 pound | 0.453592 kg |
| 1 ounce | 28.3495 g |
| 1 stone | 6.35029 kg |
Volume
| Conversion | Result |
|---|---|
| 1 US gallon | 3.78541 L |
| 1 liter | 0.264172 US gal |
| 1 cubic foot | 28.3168 L |
Frequently Asked Questions
Why does the United States still use imperial units instead of the metric system?
The US came close to fully adopting the metric system in the 1970s, but the switch was made voluntary rather than mandatory, and everyday habits, existing tools, road signs, and infrastructure kept imperial units (feet, pounds, gallons) in place for consumer use. Metric units are still used throughout US science, medicine, the military, and much of manufacturing — it's mainly everyday life where imperial units persist.
Are the conversions on this page exact, or just approximations?
They're exact. This tool uses the internationally standardized conversion factors defined by NIST and the International System of Units (SI) — for example, 1 inch is defined as exactly 0.0254 meters and 1 pound is defined as exactly 0.45359237 kilograms. These aren't rounded estimates; they're the legal definitions used worldwide for scientific and commercial conversions.
What's the difference between a US gallon and a UK (imperial) gallon?
They're genuinely different sizes — a US gallon is about 3.785 liters, while a UK (imperial) gallon is about 4.546 liters, roughly 20% larger. This split happened in 1824 when Britain redefined its gallon based on a specific volume of water, while the US kept an older English wine-gallon definition. This matters for fuel economy figures (miles per gallon means different things in the US vs. the UK), recipe conversions, and any liquid measurement figure sourced from a UK vs. US publication — always check which gallon is being used before converting.
Can I convert temperatures with this tool?
Not here — temperature conversion isn't a simple multiplication like length, weight, or volume (it involves an offset, not just a scaling factor), so it has its own dedicated Temperature Converter that instantly converts between Celsius, Fahrenheit, Kelvin, and Rankine.
Can I convert cooking measurements like cups and tablespoons here?
This tool intentionally sticks to general-purpose, engineering-style volume units (milliliters, liters, gallons, cubic feet, and similar). For recipe-specific units like cups, tablespoons, teaspoons, and fluid ounces — including the ingredient-density caveats that affect converting between volume and weight in the kitchen — use the Cooking Unit Converter instead.
Which unit system should I use for scientific or engineering work?
Metric (specifically SI units) is the standard for scientific research and most engineering disciplines worldwide because it's decimal-based and avoids the need for awkward fraction math. If you're working with US-based construction, plumbing, or consumer specifications, you'll often need to convert back and forth between systems — which is exactly what this tool is for.
