I was trying to work out how to estimate how much fuel was costing me per mile at the moment based upon my car's average mpg.

It’s not so easy because you have to convert from miles per gallon to pence per liter, not only that but it’s an imperial gallon.

Surely there’s a calculator out there that could do this for me to save me having to remember how to work it out.

There wasn’t, but I had an idea.

Recently I’ve been playing with WolframAlpha, however, I’ve found it has some garbage in garbage out issues. That is, most of the time it thinks what you’re putting in is garbage so it outputs garbage.

I soon discovered that there was a pattern to how you have to enter the calculation to get it to return the result you want.

Once I’d figured out the right instruction I discovered their “widgets”.

This lets you make a “widget” which makes it easy to enter the details to work out the calculations. This way the instruction is always the same.

You can also put the widget on your website or blog.

So here it is: