formula for calculating boxes into unit of meassure

formula for calculating boxes into unit of meassure

hi ...

i need help on how to do the following :

We sell tiles.... and invoices, quotes, etc.... are sold in Boxes.  We want to show customer how many square meter is the total of the boxes purchased.
Example ..... 1 box contains 1.44 square meter.......  so if customer buys 10 boxes = 14.40 square meter in total
i need this to be shown per individual item line.

We have created item  with square meter per box.... so the calculation should be boxes *square meter per box

If anyone has a way around to get this info, i would appretiate it.