MetricCalc unit converter
Convert Units Without Hunting for a Separate Calculator
Use this free online unit converter to quickly convert length, weight, temperature, volume, area, and speed measurements in one place.
Useful starting points
Begin With the Measurement You Already Have
Read the unit printed on the label, recipe, drawing, or document before entering its value. Choosing the correct source unit matters just as much as the number itself.
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This panel returns the result in one target unit. Choose centimeters and inches for product dimensions, or open the Length Converter for mixed formats such as feet and inches.
Drag to test nearby length values
Length Converter
39.370079
inches (in)
From
centimeters (cm)
To
inches (in)
tap a unit to make it the source
Browse by Measurement Type
Every measurement category works a little differently. Choose a category to explore the right units, practical explanations, and direct unit converter tools for the type of measurement you need.
Length Converter
Compare dimensions and distances across metric and imperial units, from millimeters used in drawings and product specs to miles used for road distances and travel.
Explore the length converterWeight Converter
Convert package weights, body weight, recipe ingredients, and laboratory masses while keeping grams, kilograms, pounds, and ounces clear and easy to compare.
Explore the weight converterTemperature Converter
Convert temperature readings between Celsius, Fahrenheit, Kelvin, Rankine, Réaumur, and scientific reference points such as the triple point of water.
Explore the temperature converterVolume Converter
Convert liquid quantities for recipes, containers, bottles, and larger capacity measurements, with separate options for US gallons and imperial gallons.
Explore the volume converterArea Converter
Compare room sizes, floor plans, property measurements, and land areas using square units, acres, hectares, and other common area measurements.
Explore the area converterSpeed Converter
Convert travel speed, running pace, nautical speed, and engineering motion rates across common metric, imperial, road, and marine speed units.
Explore the speed converterPopular Conversions by Category
Weight Converter
Length Converter
Temperature Converter
Volume Converter
Area Converter
Speed Converter
Choose Units That Fit the Task
A conversion can be mathematically correct and still be difficult to use if it relies on the wrong unit, definition, or level of precision. Before using any online unit converter, check where the original measurement comes from and how the converted result will be used.
| Task | Better starting point | Why it helps |
|---|---|---|
| Ordering furniture from another country | cm to inches | Convert each dimension separately and keep the original length × width × height order unchanged. |
| Adapting a recipe from another region | cups to milliliters | Check whether the recipe uses US, metric, or imperial cups before measuring or converting ingredients. |
| Comparing land listings | square meters to acres | Use acres and hectares to compare large land areas more clearly than long square-meter values. |
| Driving in another country | kmph to mph | Compare the converted speed with the road sign instead of relying on a rough mental estimate. |
| Preparing precise technical dimensions | meters to millimeters | Keep the full, unrounded value during the calculation, then round only when you record the final measurement. |
Read the Unit Label Before Using the Result
Similar abbreviations do not always refer to the same type of measurement. Fluid ounces measure volume, while ounces usually refer to weight. A metric tonne is different from a US short ton, and a knot means one nautical mile per hour. Reading the full unit name helps prevent a reasonable-looking result from being used in the wrong context.