Inventory Quantity Standards
Inventory
Quantity Standards
1. Ordering Level or Ordering Point or
Re-ordering Level:
This is that
level of material at which a new order for supply of material is to be placed.
In other words, at this level a purchase requisition is made out. This level is
fixed some where between maximum and minimum levels. Order points are based on
usage during time necessary to requisition order, and receive materials, plus
an allowance for protection against stock out.
The order point
is reached when inventory on hand and quantities due in are equal to the lead
time usage quantity plus the safety stock quantity.
The following
two formulas are used for the calculation of re-ordering level or point:
(i) Ordering
Point or Re-order level = Maximum daily or weekly or monthly usage × lead time
(Lead time would
mean the time required to get fresh or new supply of material)
The above
formula is used when usage and lead time are known with certainty; therefore,
no safety stock is provided.
When safety
stock is provided then the following formula will be applicable:
(ii) Ordering
point or Re-order Level = Normal daily or weekly or monthly usage × lead time + Safety Stock.
2. Minimum Level or Minimum Limit:
The minimum
stock or level is the lowest level to which the inventory should be allowed to
fall. It is the cushion stock which allows some margin of safety.
In other words,
the minimum level is that level of stock below which stock should not normally
be allowed to fall. In case of any item falling below this level, there is
danger of stoppage of production and, therefore, the management should give top
priority to the acquisition of new supplies.
Minimum level or
limit may be calculated as follows:
Minimum Limit or
Level = Re-order Level or Ordering Point – Average or Normal Usage × Normal reorder period
Or it can be
written as follows:
Minimum Level =
Reorder Level – Average usage for normal reorder period.
3. Maximum Level or Maximum Limit:
The maximum
stock limit is upper level of the inventory and the quantity that must not be
exceeded without specific authority from management. In other words, the
maximum stock level is that quantity of material above which the stock of any
item should not normally be allowed to go. This level is fixed after taking
into account such factors as: Capital available, rate of consumption of
materials, storage space available, insurance cost, risk of deterioration and
obsolescence, and Economic order quantity.
The maximum
level or limit may be calculated by the help of following formula:
Maximum Limit or
Level = Reorder Level – minimum usage × minimum reorder period + Economic Order
Quantity.
4. Danger Level:
Some enterprises
also calculate ‘danger level’. When this level of stock is reached, then
emergency steps are taken by the management to acquire material supplies. When
this level is reached, the try is made to purchase materials from the nearest
possible source or place so that the workers and plant and machinery may not
remain idle due to shortage of material supplies. It may be calculated as
follows:
Danger Level =
Average daily requirement × time required to get emergency supply.
5. Economic Order Quantity
economic Order
Quantity is that size of the order which gives maximum economy in purchasing
any material and ultimately contributes towards maintaining the material at the
optimum level and at the minimum cost. In other words, the Economic Order
Quantity is the amount of inventory to be ordered at one time for purposes of
minimising annual inventory cost.
The quantity to
order at a given time must be determined by balancing two factors (1) the cost
of possessing (carrying) materials and (2) the cost of acquiring (ordering
materials). Purchasing a larger quantities may decrease the unit cost of
acquisition, but this saving may not be more than offset by the cost of
carrying materials in stock for a longer period of time.
The carrying
cost of inventory may include:
Interest on
investment of working capital; property tax and Insurance, storage cost,
handling cost, deterioration and shrinkage of stocks, obsolescence of stocks.
The different
formulas have been developed for the calculation of Economic Order Quantity.
The following
formula is usually used for the calculation of Economic Order Quantity (E. O.
Q):
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