GIFSQ Tools · Module 18 — Manufacturing, Costing & Supply Chain · Tool 343 of 500
Work out the net raw material to buy for a production plan: gross requirement from the planned output, less the stock on hand, plus the safety stock you want to keep — the core of material requirements planning (MRP).
Try sample values — fills the form with the worked example below.
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Gross requirement (kg)
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Net requirement to buy (kg)
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Stock cover (units)
Equation: Gross requirement = planned production × material per unit. Net requirement = gross − stock on hand + safety stock, floored at 0. Stock cover = stock on hand ÷ material per unit.
Method: Netting in material requirements planning (MRP): the gross requirement is the total material the plan consumes; stock on hand is netted off, and the safety stock is added back so the warehouse is not emptied. A negative net requirement means no purchase is needed.
Assumptions: the usage per unit is constant; stock on hand is usable stock (not quarantined or expired); lead time is not considered — use Tool 350 for the order timing.
Limitations: the tool plans one material at a time and does not split the order across suppliers or pack sizes; scrap and yield loss are not included — add them to the usage figure first.
Rounding: requirements to 2 decimal places; stock cover to 1 decimal place; intermediates unrounded.
This is a calculation aid, not a laboratory report — confirm against your accredited method before citing a value.
Method: Netting in material requirements planning (MRP): the gross requirement is the total material the plan consumes; stock on hand is netted off, and the safety stock is added back so the warehouse is not emptied. A negative net requirement means no purchase is needed.
Assumptions: the usage per unit is constant; stock on hand is usable stock (not quarantined or expired); lead time is not considered — use Tool 350 for the order timing.
Limitations: the tool plans one material at a time and does not split the order across suppliers or pack sizes; scrap and yield loss are not included — add them to the usage figure first.
Rounding: requirements to 2 decimal places; stock cover to 1 decimal place; intermediates unrounded.
This is a calculation aid, not a laboratory report — confirm against your accredited method before citing a value.
Worked example: Planned production 500 units at 2.5 kg each, 300 kg on hand, 100 kg safety stock: gross = 1,250.00 kg; net = 1,250 − 300 + 100 = 1,050.00 kg to buy; stock on hand covers 120.0 units.
Enter values above to see results.
If the net requirement is 0, the plan is fully covered — check the expiry dates of the stock on hand before relying on it. Tool 343 of 500 — GIFSQ
