When you have a web site your pages will be read by people from around the world. While most of the world uses the metric system of measurements there are still a few countries that have yet to convert to this far more sensible system. Until these countries change over there will be some pages that give information in metric measurements and some that use other measurements. If you are not familiar with the other measurement system then converting the values shown into something you can understand can be difficult.
When you are providing measurement information on your site you can make things easier for your visitors by providing them with a calculator that can perform these conversions to and from metric measurements for them.
To save you the effort of creating such a calculator, I have written one for you that can be easily added to your web page. Try out this metric calculator for yourself to see if it would make a useful addition to your site.