Hi, use sales/purchase units. it works well. manufacture what you would by. sell sales units or purchase units. it is working ok. tested.

Hello Toni,

You have to use of BoM type: kit.

You have to create one extra product for that and inside this extra product BoM(kit) set the actual product which you want to sale in kg.

And generate the sale order then it is works well.

If you have any queries then contact us on shivoham.odoo@gmail.com

As far as i know the is no conversion between unit category you have to build your own rules to mix unit categoy and convert  KG in unit or meter  if know the way to convert it  for sample a 15000 Kg roll of paper could be convert in meter (the lenght if you know 

thickness,Weight and width of this roll... ( and so create those fields  in odoo to use it )

 so it depend of what you want to do add apply rule depending on category product or many other criteria

Hope this help