This calculator is for newbie web developers that may need help with html forms and validating/processing with PHP. I's also for css developers who don't want to whip out their calculator.
What is an em unit?
In CSS, an em unit is equal to the computed font-size for the element to which an em is applied. When em units are declared on child elements that don’t have a font-size defined, they will inherit their font-size from their parent, or from another ancestor element, possibly going all the way back to the root element on the document.
To calculate your em unit enter your Base Font Size then your Target Pixel Size and click on the convert button.