Anyone good at maths?!!

Hi Scentia and Farmor I can help but as the saying goes, I know someone who can (i.e. he has a brain). DHs figures are the same as yours Farmor and he agrees with your totals if that helps ?

Sorry I couldn't help , the problem brought back the dread I feeling at school with trains travelling at certain speeds and filling baths with a certain amount of water. I am glad someone else could help.

Hope my calculations are correct! I don't know where you'll be sourcing your topsoil and compost, but for that amount, it will probably be cheaper to get it by trailerload, rather than bags.

That is so helpful, thanks very much.

First thing to realise is that these beds will need a lot of topsoil/compost.
I did a quick calculation and came up with the following:
Volume of bigger beds 180x60x30 = 324000 cubic cm or 324 liters. x4= 1296 l.
Smaller beds 120x30x30=108000 cubic cm or 108 liters. x2= 216 l.
Total volume needed 1296 + 108 = 1512.
70% topsoil 1512 x0.7 = 1058 or roughly 1000 litres - probably about a metric tonne.
30% manure/compost 1512x 0.3 = 453 l. Probably 1/2 tonne.

Hope this helps! Seems like a lot?