ASC Software

Master Production Schedule (MPS) Calculator

Enter your forecast and customer orders and see what to produce each period, what inventory you will hold, and how much you can still promise.

How to use this calculator

  1. Enter what you have in stock and your planning rules.
  2. Type your forecast and the customer orders already booked for each period.
  3. Press Calculate to see what to produce, the inventory you will hold, and how much you can still promise.

New here? to see how it works. Blank cells count as 0.

1. Your stock and rules

Units in stock right now.

The minimum you want to keep on hand.

Batch size. Blank = make exactly what is needed.

Near-term periods that use customer orders only. Use 0 if unsure.

How many weeks (or days or months) to plan.

2. Demand by period, then results

Type in the white boxes. The shaded rows are calculated for you.

Master production schedule: forecast and customer orders by period, with planned production, projected on-hand and available to promise.
RowPeriod 1Period 2Period 3Period 4Period 5Period 6
ForecastYour sales forecast. You enter this.
Customer ordersOrders already booked. You enter this.
Demand usedThe higher of the two.
Planned production (MPS)What to make each period.
Projected on-handStock left at the end of the period.
Available to promiseStill free to promise to new orders.

How the calculation works

For each period the calculator works out demand, decides whether a production lot is needed to stay at or above your safety stock, and carries the inventory forward:

  • Demand used = the greater of forecast and customer orders. Inside the demand time fence it is customer orders only.
  • Planned production (MPS) = enough lots to keep projected on-hand at or above safety stock. With no lot size, it produces exactly the shortfall (lot-for-lot).
  • Projected on-hand = previous on-hand + planned production − demand used.
  • Available to promise (ATP) = planned production − customer orders due before the next production lot. Period 1 also adds the starting on-hand.

Worked example

Start with 40 units on hand, a safety stock of 10 and a lot size of 100. Period 1 forecast is 60 but customer orders are 75, so demand used is 75. On-hand would fall to −35, which is below safety stock, so one lot of 100 is planned: 40 + 100 − 75 = 65 projected on-hand. In period 2, demand of 70 leaves 65 − 70 = −5, so another lot is planned and projected on-hand becomes 95. Period 3 demand of 80 is covered from stock (95 − 80 = 15), so no production is planned. Use the Load example button to see the full six periods.

ATP for period 1 is the starting 40 plus the 100 lot, less the 75 already promised before the next lot lands: 65 units still available to promise.

When available to promise is negative

ATP only counts the lot planned in that period. If customer orders due before the next lot are larger than the lot, ATP goes negative. It does not mean the orders can't be met, because projected on-hand from earlier lots may be covering them. It means that, looking at this lot alone, the window is over-promised. The calculator shows the negative value and flags the period rather than quietly carrying it back to an earlier lot, which some textbooks do. If your course or planning system uses cumulative ATP, expect different numbers in later periods.

What this calculator leaves out

It does not apply production lead time, capacity limits or a frozen window, and it plans one item at a time. Lead-time offsetting happens in the next step, material requirements planning. For how the MPS fits into the planning chain, read Master Production Schedule (MPS): What It Is, How It Works, and How Software Manages It.

To see how ASC Software supports production scheduling, explore ASC's production scheduling or ASC's Manufacturing Execution System (MES).

This calculator is for estimation and education. Results depend on the planning rules above and may differ from your own planning system.

Questions about planning your production?

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