How much Gravel do I need

[Broadie451]

I posted this question in gardening but I have been advised to post it in DIY too.
how much gravel do I need to cover 20sq meters of border, at the moment we have bark but the chickens from next door perform a sort of dawn raid for worms and scatter the bark everywhere, plus is going a little soggy.

Many thanks for your help.

[alavahalf]

How deep do you intend laying the gravel... say 2'' or 50mm..that would be 1 cubic metre required.

[Jemisa]

I think I warned you about the cats before B451 they do love a bit of gravel to do their business in, they think its a giant cat-litter tray.