Hi,
Hope this helps.
Go to this site and look up the heading "Tank Volumn calculator."
www.firsttankguide.net/capacity.php



Rick




"Steve"  wrote in message 
news:0rypi.1003$h11.497@newsfe7-gui.ntli.net...
> Hi,
>
> My rather old tank is 48" * 18" * 12-15" (Sloping Front).
>
> I can get the size in cubic inches = 48 * 18 * (12+15)/2 = 11664.
>
> How do I convert this to Litres so I know what capacity external filter
> to get?
>
> My existing Hydor Prime 20 filter is getting older, slower and now makes
> a lot of noise but doesn't move much water even after a clean and new 
> media.
>
> Any recommendations? I'm after something easier to open, easier to prime 
> and as quiet as possible.
>
> Thanks, Steve