The paper presents an approach to allocate joint costs to production branches based on maximum entropy. Using bookkeeping data from the Farm Accountancy Data Network (FADN) we derive full product costs. Accordingly, the suggested approach offers the opportunity of full product costs based on actual costing rather than normal costing. The approach is applied for arable crop in Switzerland providing full product costs on a hectare base. The resulting total costs are up to 20 percent higher than in literature. An important reason is labour, which shows for all analysed production branches higher costs than in the actual costing based literature.