Conversion Calculator – Convert Common Units Online
Convert common units of length, mass, volume and temperature in one place.
About the Conversion Calculator
What is the Conversion Calculator?
A conversion calculator changes a value from one unit to another across the most common everyday measures: length, mass, volume and temperature.
Why use this calculator?
Recipes, travel, DIY projects and homework constantly mix metric and imperial units, and a reliable converter avoids costly mistakes.
How to use it
- Enter the value you want to convert.
- Choose the unit you are converting from.
- Choose the unit you are converting to and read the result.
Formula
value × factor(from) ÷ factor(to) in the shared base unit. Temperature uses offsets instead of a simple factor.
Pick units of the same type — temperature units convert only to other temperature units.
Frequently Asked Questions
Why can I not convert litres to kilograms?
Litres measure volume and kilograms measure mass. They are different physical quantities, so a fixed factor does not exist without knowing the density of the substance.
How many millimetres are in an inch?
Exactly 25.4 millimetres, which is the international definition of the inch.
How precise are the conversions?
Conversions use standard, internationally defined factors and are rounded for display. They are accurate to the number of digits shown.
Can I convert back and forth without losing accuracy?
Yes. Enter the original value to get an exact inverse conversion; avoid chaining rounded results if you need maximum precision.
Which measurement system is used?
Both metric (SI) and US customary / imperial units are supported and clearly labelled.
Is this calculator free to use?
Yes. Every calculator on this site is completely free, with no hidden fees, no subscriptions and no limits on how many times you can use it.
How accurate are the results?
We use standard, widely accepted formulas and calculate in your browser using double-precision arithmetic. Results are rounded for readability, so treat them as reliable estimates rather than a guarantee. Real-world factors can vary the true figure.
Can I add this calculator to my own website?
Yes. Open this calculator page and use the "Add to your website" box in the sidebar to copy a ready-made iframe snippet, then paste it into any HTML page.
Does it work on a phone or tablet?
Yes. The layout is fully responsive, so it works on desktops, laptops, tablets and mobile phones, and every input adapts to touch screens.
Is the information I type kept private?
Yes. All calculations run locally in your browser. Nothing you enter is uploaded, stored or shared with anyone.