Formulas of MPR

This paper presents MRP in formulas. The usual presentations of the MRP-calculation in textbooks for operations management and production economics in tables are described here in formulas. In the MRP-calculation: first MRP reschedules already open orders to current gross requirements, then MRP calculates and time-phases planned orders to satisfy the remaining gross requirements. The MRP-calculation can face an open order with a planned due date in the past time, and where the real due date will be in the future. Such problems are seldom pointed out in textbooks, but the presented formulas must handle it and similar problems. The paper tries to postulate the ‘real’ MRP-calculation. It is important that the paper defines what it really means when the paper talks about MRP. The formulas are on an excellent method for communications. Furthermore the paper points to the connections between MRP and input-output analyses. Definitions of inefficiences are related to MRP, ‘remnant stock’ and ‘imbalance’, are discussed with the formulae used.