How do you convert children's shoe sizes to adult?

Here's a link to a nice conversion chart. http://www.bata.com/documents/pdf/size_chart_printable.pdf It seems like the EU (French) system is the most foolproof because the sizes go up by 6.6mm each increment. (Other systems seem to be comparatively arbitrary) In other Words, look at your children's shoe size on the tongue of the shoe. Hopefully it will have the EU size listed too. Refer to the chart and find your EU size on the "French" scale. From there you should be able to convert your shoe size to anything.