Net Requirements Calculator
Net requirements are the units you actually have to make or buy once existing supply is counted. Enter gross requirements, inventory on hand and scheduled receipts for one item and one period, and this calculator nets them into a single shortfall figure, floored at zero when stock already covers demand.
One item, one period per run. Blank and non-numeric entries count as zero, and the result never drops below zero. This tool nets demand only: it does not add safety stock or allocations, and it does not lot-size or offset for lead time.
Quick Answer
Net requirements = gross requirements – (inventory on hand + scheduled receipts), never below zero. With gross requirements of 1,000 units, 200 on hand and 300 already on order, the net requirement is 500 units: that is the quantity a new planned order has to cover for this period.
Key takeaways
- Netting runs per item and per period. A surplus in one week becomes next week’s on hand, not a reason to skip the next run.
- A zero result is a real answer: supply covers demand, and ordering more only ties up cash and shelf space.
- This is the basic textbook formula. Safety stock and allocations sit outside it, so add them to gross requirements if your policy holds a buffer.
- The output is a shortfall, not an order. Lot size rules and lead time turn it into one.
- Quick Answer
- How to use the net requirements calculator
- The net requirements formula, and what it leaves out
- Worked example: 1,000 gross nets to 500
- Running netting period by period
- Where netting goes wrong in practice
- What competing calculators miss
- Frequently asked questions
- Add This Calculator to Your Website
- References
How to use the net requirements calculator
Three inputs and one click: the tool nets a single item for a single planning period.
- Gross requirements: the period’s total demand for the item, from firm orders, the master production schedule, or dependent demand exploded from parent items.
- Inventory on hand: usable stock at the start of the period. If your count includes units reserved for other orders, either subtract them here or add them to gross requirements, but never count them twice.
- Scheduled receipts: open purchase orders and released shop orders due inside the period. Only firm orders belong here.
- Calculate: the result is the shortfall a planned order must cover, plus a covered or shortfall reading. Use Copy or Share to pass the figure to a buyer or planner.
Run it again for the next period with any surplus carried into the on hand figure. Planners who track inventory variance between book stock and physical counts will get more from this tool than planners who net against numbers nobody has verified.
The net requirements formula, and what it leaves out
The formula is one subtraction with a floor: net = gross – (on hand + scheduled receipts), and if that goes negative the net requirement is 0.
Gross requirements are demand before netting. In an MRP run they come from the master schedule for end items and from planned order releases of parent items for components, a process textbooks call gross-to-net calculation. On hand is the supply you can touch today; scheduled receipts are supply already committed. Oracle’s MRP documentation frames the same logic as projected on hand: current supply (nettable on hand plus scheduled receipts) minus gross requirements, with a negative projected balance signalling the shortage a planned order must fix (see References).
One honest limit belongs here. The full ASCM definition of net requirements also applies allocations and safety stock: net = gross + allocations + safety stock – on hand – scheduled receipts. Allocations are units already promised to other orders; safety stock is the buffer you refuse to plan below. This calculator, like most simple netting tools and most course examples, omits both. If your operation holds safety stock, add it to the gross requirements input and the result stays correct for the basic model.
Worked example: 1,000 gross nets to 500
The worked example is the pre-filled run: gross 1,000, on hand 200, scheduled receipts 300, net requirement 500.
Gross requirements
On hand
Scheduled receipts
Net requirements
Four more runs, each checked in the tool, show the shape of the answer across normal planning cases:
| Case | Gross | On hand | Scheduled | Net | Reading |
|---|---|---|---|---|---|
| Worked example | 1,000 | 200 | 300 | 500 | Shortfall |
| Thin stock, nothing inbound | 2,400 | 350 | 0 | 2,050 | Shortfall |
| Over-covered period | 800 | 500 | 450 | 0 | Covered, 150 surplus |
| Fractional quantities (kg) | 1,250.5 | 300.25 | 100.25 | 850 | Shortfall |
The fractional row is worth a second look. The tool does no rounding, so counts in pieces stay exact and weights in kilograms keep their decimals. With awkward decimals the raw output can show full floating-point length (0.3 – 0.1 displays as 0.19999999999999998); round that display in your own records, because the underlying shortfall is 0.2.
Running netting period by period
Real MRP repeats this one calculation across the horizon, carrying the projected balance forward each period.
Start each period with the previous period’s leftover. If supply covers gross requirements, the surplus rolls into the next period’s on hand. If it does not, the shortfall is that period’s net requirement and a planned order receipt is assumed to land inside the period, which is why the following period starts from zero rather than from a negative balance. A three-week run for one component shows the pattern:
| Week | Gross | Beginning on hand | Scheduled receipts | Net requirement |
|---|---|---|---|---|
| Week 1 | 600 | 250 | 100 | 250 |
| Week 2 | 450 | 0 | 200 | 250 |
| Week 3 | 300 | 0 | 350 | 0 (50 surplus carries out) |
Each row reproduces in the calculator exactly as shown. What the table cannot show is timing inside the week: a scheduled receipt landing on Friday does not cover a requirement due Monday, which is why full MRP systems bucket by day or week and offset planned orders by lead time.
Where netting goes wrong in practice
Most bad net requirements are bad inputs, not bad arithmetic. Three failure points account for nearly all of them.
Stale on hand. Book stock drifts from physical stock through scrap, damage, mis-picks and unrecorded issues. A planner netting against phantom inventory discovers the shortage on the line, at the worst moment. Cycle counting and watching inventory shrinkage percentage keep the on hand figure honest.
Optimistic scheduled receipts. An order due this period that slips two weeks turns a covered plan into a stockout. The cost of that miss is not abstract: expediting fees, line stoppages and lost sales are exactly what a cost of understocking estimate puts a number on. Net with confirmed ship dates, not hoped-for ones.
Double-counted reservations. Stock allocated to a firm order cannot also cover new demand. Either exclude allocated units from on hand or include the allocation on the demand side, as the full ASCM formula does. Doing both, or neither, corrupts the result in opposite directions.
What competing calculators miss
Search this term and you mostly find explainers, not tools, and the tools that exist tend to blur the model they are running:
- Course and reference pages (ERP Information, university MRP notes, textbook chapters): strong on the full model, including the ASCM formula with safety stock and allocations, multi-period tables and projected available balance. Gap: no calculator at all, so the reader nets by hand or in a spreadsheet.
- MRP tools that start from planned orders (CalculatorsHub and similar): they compute a planned order release from safety stock, on-order and work-in-process inputs. Useful downstream, but that is a different quantity from net requirements, and the page presents the two as if they were the same step.
- ERP suites (Oracle, SAP): complete netting with allocations, pegging and time-phased records, at enterprise cost and complexity. A planner checking one item for one period does not need a login and a planning run.
- The gap this page fills: the plain gross-to-net calculation as an instant tool, with the zero floor, a covered versus shortfall reading, period-by-period carryover shown with real numbers, and the safety stock limitation stated on the page instead of buried.
Frequently asked questions
Net requirements are the units you still need to produce or order for one item in one period after counting what you already have. The calculator subtracts inventory on hand and scheduled receipts from gross requirements and floors the answer at zero, so a covered period reads 0 rather than a negative number.
Net requirements = gross requirements – (inventory on hand + scheduled receipts), with a floor of zero. Example: 1,000 gross – (200 on hand + 300 scheduled) = 500 net. That basic gross-to-net form is the version taught in operations courses and used as the first netting pass in MRP systems.
The tool shows 0. A negative raw result means on hand plus scheduled receipts already cover the gross requirement, with stock left over. That leftover becomes beginning on hand for the next period, which is why planners run the same calculation period by period instead of once for the whole horizon.
No. This tool runs the basic netting formula only. The full ASCM definition also adds safety stock and allocations (stock reserved for other orders) to the demand side: net = gross + safety stock + allocations – on hand – scheduled receipts. To approximate that here, add your safety stock and allocated units to the gross requirements figure before calculating, and say so in your planning notes.
Scheduled receipts are firm, already-released orders due in the period: open purchase orders and released production orders. A quote, a planned order the system has only suggested, or a supplier promise with no order behind it does not count. If a scheduled receipt slips to a later period, move it out of this period’s figure or the net requirement will be understated.
Yes, one run per item per period. Netting is item-specific because on hand and scheduled receipts belong to a single part number, and period-specific because leftover stock carries forward. Run week 1, carry any surplus into week 2 as on hand, and repeat. The period table in the worked sections shows that carryover pattern with real numbers.
No, and that is deliberate. Netting answers how much is short. Lot sizing decides how much to order (lot-for-lot, fixed quantity, minimum order), and lead-time offsetting decides when to release it. Those are the two MRP steps that follow netting, and they need your supplier and production rules, which a three-input tool cannot know.
Any consistent unit: pieces, cartons, kilograms or litres. The tool is unit-agnostic and does no conversion, so all three inputs must use the same unit for the same item. Mixing cases on one line and pieces on another is the most common silent error in hand-run netting.
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References
- Rossetti, M. D. Analysis of Inventory Systems, Chapter 6: Material and Distribution Requirements Planning (net requirements as max(gross + safety stock – scheduled receipts – previous on hand, 0)). Accessed October 22, 2026.
- Oracle. Oracle MRP User’s Guide: projected available balance and projected on hand definitions. Accessed October 22, 2026.
- Oracle. Oracle Project Manufacturing Implementation Guide: MRP netting and projected available example. Accessed October 22, 2026.
- Heizer, J. and Render, B. Operations Management, Chapter 14: Material Requirements Planning (lecture slides, King Saud University). Accessed October 22, 2026.
- SAP. SAP Library: Net Requirements Calculation (MRP netting in the planning run: requirements are checked against plant stock and fixed receipts already planned, and a shortage creates a procurement proposal). Accessed October 22, 2026.