Compare the target value with every equivalent
The reference list expresses the same entered quantity in every supported unit for the active category. It is a quick check before you copy a number into a plan or note.
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Free Unit Converter Online
Convert metric and imperial length, weight, temperature, and US volume units online. See the formula and equivalent values instantly without registration.
- • Metric and customary units
- • Length, weight, temperature, volume
- • Formula and equivalents
- • Runs in this browser
Convert a measurement
Pick one category so both units measure the same quantity. The result and reference values update in this browser.
Quick conversions
Free online, no registration or login. Values stay in this browser while the conversion runs.
Your converted value will appear here
Enter a number, then choose compatible source and target units.
How to convert units
The category keeps units compatible before you compare the number and the formula.
- Step 1
Choose a measurement category
Select length, weight, temperature, or volume. The source and target lists only contain units that describe the same kind of quantity.
- Step 2
Enter a value and two compatible units
Use whole numbers or decimals, then choose the source unit and the unit you want to read. Swap the direction whenever you need the reverse conversion.
- Step 3
Check the result before you use it
Review the target value, the formula or base relationship, and the all-equivalents list. Round only to the precision appropriate for your task.
How to check a unit conversion
The direct answer is useful when you know a target unit. A formula and same-category equivalents make it easier to check that the input and units match the decision you need to make.
Read the formula used
Length, weight, and volume use a canonical base relationship. The result panel names that base; temperature shows an offset formula instead of pretending it is a simple ratio.
Round only for the decision you need to make
A displayed decimal is a readable representation, not a statement about the accuracy of the original measurement. Keep appropriate significant figures for the source you have.
Metric, customary, and temperature rules
Measurement systems use different named units, but conversions should preserve the same quantity. Some relationships are defined; others need special context and should not be guessed.
Use defined base relationships
The converter reduces supported length values to meters, weight values to kilograms, and US volume values to liters before expressing the same quantity in another compatible unit.
Temperature needs an offset formula
Celsius, Fahrenheit, and Kelvin do not share a common zero. The tool converts through Celsius with the appropriate offsets and scale relationship.
US volume units are labelled explicitly
A gallon, quart, pint, cup, and fluid ounce here use US liquid measures. Do not treat these outputs as an imperial-gallon or recipe-weight substitution.
Everyday conversion checks
These controls help translate a stated measurement. They do not decide which unit a regulation, manufacturer, recipe, or instrument requires.
Length for plans and travel
Convert meters, kilometers, centimeters, inches, feet, yards, miles, or nautical miles when you need a compatible distance representation.
Weight for products and fitness
Convert kilograms, grams, milligrams, pounds, ounces, stone, tonnes, or short tons. The tool treats the everyday word weight as mass units for conversion.
Temperature and volume for everyday references
Switch weather or equipment temperatures between Celsius, Fahrenheit, and Kelvin, or compare liters and US liquid volume units without using an external rate or account.
Privacy and limits
Your value and selected units stay in this browser while the calculator runs. This free online tool requires no registration or login.
- The converter supports common length, weight, temperature, and US liquid volume units, not every scientific, engineering, data, currency, or cooking-measure convention.
- Displayed values are rounded for readability; the source measurement’s precision, calibration, and significant figures remain your responsibility.
- This browser calculation is not a substitute for a required legal, medical, safety, laboratory, commercial, or manufacturer-specific measurement standard.
Unit Converter FAQ
Answers about metric and customary units, temperature formulas, display rounding, and this tool’s scope.
How do I convert one unit to another?
Choose a measurement category, enter a number, then choose the source and target units. The result and all supported equivalents update in the browser.
Can I convert metric to imperial and back?
Yes. The tool supports common metric and customary length, weight, and US volume units in both directions.
Is 1 inch exactly 2.54 centimeters?
Yes. The international inch is defined as exactly 2.54 centimeters, so the converter uses 0.0254 meter for one inch.
How many pounds are in a kilogram?
One kilogram is about 2.20462262 pounds. The tool calculates from the defined avoirdupois-pound relationship before rounding the display.
Why do temperature conversions use a formula?
Celsius, Fahrenheit, and Kelvin have different zero points as well as different interval sizes. A temperature conversion needs an offset formula, not only a multiplier.
Can I convert Celsius, Fahrenheit, and Kelvin?
Yes. Select Temperature, then choose any two of Celsius, Fahrenheit, and Kelvin.
Is a US gallon the same as an imperial gallon?
No. This tool labels and uses US liquid gallon units only. It does not present an imperial-gallon result as interchangeable with a US gallon.
Why are some results rounded?
The workspace calculates with JavaScript numeric precision and rounds the displayed value for readability. The all-equivalents list uses the same source value.
Is this unit converter free online without registration or login?
Yes. This calculator is free to use online and does not require registration or login.
Does this tool upload my measurement?
No. Your value and selected units are calculated in this browser tab.
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