How many tiles do I need?

[lizwizz]

I'm trying to work out how many tiles I need to tile the bathroom wall and floor. I thought it would be easy, but there are so many bits here and there and bits that aren't going to be there when the bathroom is finished. Is there a relativley easy method and how accurate do I need to be?
Thanks

[Mattk]

simply measure the area ignoring the fact that some points within that area will not need covering then simply by dividing the size of the desired tile into your measurements an answer will be given!

its always best to have spares anyway in case of damage etc

[lizwizz]

Thanks Matt, I hadn't thought of the spares!

[chazza]

If in doubt, over estimate. Most DIY shops will give you a refund on unopened packs. Check when paying though!