For each product, you can select from the following unit types: Each, Box, Case, Pallet, Oz, Lb, Gr, Kg or Hours.  

To convert from one unit to another when purchasing, you can use “Order Pack” to determine the conversion unit. For example, if you sell wine by the bottle, but purchase by the case of 12, you would set up your product UOM as Each on the Product Info page, then enter 12 for the Order Pack Qty under the Purchasing Info page.  When you purchase this item, it will automatically come up as 12 units.

You can also create Bundles that have fractions of individual units if you use partial amounts in the assembly of finished goods.