I know that buying garments for women is a bit of a minefield, what with vanity sizing and all, but sewing garments for children from commercial patterns is no less tricky. Especially if your child is not a 'standard' size - my daughter for example is all round dinky with very short legs (alas! her mummy's genes won through there!) while my son is of average height but super-skinny.
And if you're sewing garments to sell, it's even worse! I never know how to label mine and generally end up erring on the side of caution. I recently bought a Japanese pattern book and want to make a Communion dress from it for the shop but I wasn't sure what size to go for. So... I put together a sizing comparison chart. It might look like a procrastination task but it's actually been very useful. I shall be passing it onto my sewing pupils and thought that you might find it handy too. So here's the link - Sizing Comparison Chart. Now you may wonder why I haven't just included it in the blog post - the answer is I created it as a Word document and can't just paste it into the blog. So I resaved it as a PDF and posted it on Google Docs instead - that way everyone can download and print it, no matter what version of Word they may be running. And it also means that I can never lose it... yes, there really is no such thing as altruism!