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NPMA 21Volume 14, Issue 2 – 2002 © 2002 National Property Management Association

Total cost of ownership is an assessment of all costsinvolved with an item over its useful life. Typically,it is calculated at the beginning of the purchase

process to determine the most cost-effective choice. Atthis point, many of the costs included are estimates, sincethey have not yet been incurred.

Calculating the total cost of ownership can give anorganization better information with which to make thepurchasing decision. Many purchasers know instinctivelythat quoted price is not the only cost that will be involved

in obtaining and using an item. Inclusion of all otherknown cost factors allows a more complete picture toemerge.

Many cost factors are known only to users or others inthe organization. The most complete picture will be com-piled by a team composed of purchasing plus at least theusers, technical experts and finance. Insuring that allinvolved parties have the chance to participate is importantto achieving a useful result.

Define the ground rules and assumptions which willguide the work, including:

Definition of what is needed and who will use it

Estimate of how long the item will be in use Assumptions for quantities or consumption rate

Definition of the process for defining the areas of costto be included

Definition of the process for calculating cost figures forthese areas

Estimates of cost elements (such as the cost of carryinginventory)

The elements of cost will bedifferent for inventory or stockeditems versus capital equipment.

Inventoried items are of lower dol-lar value per unit, but higher vol-umes. Inventory items also aremoving through the business.They are regularly turned over.Capital equipment is stationaryand may be in place for a longtime. Typical areas included in thetotal cost of ownership for each of these include:

How to appro ach calculation o f the To tal Co st

of Ownership:

The steps in determining the total cost of ownership are:

1. Form a team composed of purchasing, users, technicalexperts and finance. Add others as appropriate.

2. Define the ground rules for the process and theassumptions listed above.

3. Define the areas of cost that the team believes are rele-vant to this purchase or item.

4. Work out reasonable methods for calculating costs forthe areas you have identified. Calculate those costs.

5. Sum all relevant costs. Make your decisions based oncalculation of the total cost of ownership.

Total cost of ownership data is typically used to makea better choice of suppliers or of items to be purchased. Itcompares Supplier A to Supplier B or Item X to Item Y. If the calculations are used for relative comparisons, you canbe somewhat more relaxed in determining costs. Estimatesare acceptable as long as they are relatively valid. In otherwords, they provide a valid basis for comparison. Two cri-

teria are important when calculating relative costs:1. That the formula makes sense. It is relevant to the issue

and can be calculated.

2. That the formula can be applied across suppliers andused to validly differentiate them

If total cost of ownership is used to make capital allo-cation decisions, then there will be more stringent restric-tions on assumptions and more urgency to use only verifi-

Calcu lating The To tal Co s t o f Own e rshipFo r Ite m s Which are Inve nto rie d

B Y MAR Y LU H AR DING , C.P.M., CP IM, CIR M

INVENTORY CAPITAL EQUIPMENTCost of non-delivery Structure of payments over time

Cost of non-quality Packing & crating costsCost of transportation & packaging Cost of transportationCost of carrying inventory Cost of site modificationsProduction-related costs Cost of rigging & installationAdministration costs per part number Technical assistance at start-upAvailability / flexibility Operator trainingTechnical assistance Cost of service & maintenance

Cost of supplies and spare partsTrade-in value of old equipmentEstimated useful life of new equipment



able dollar figures. Numbers will be required to beabsolutely accurate, not just relatively accurate. The degreeto which you can use relative versus absolute cost datashould be defined as one of the starting assumptions.

Ownership costs can be divided into three categories:incurred costs, performance costs and policy costs.Incurred costs are ancillary charges for which you will bebilled (i.e. transportation, spare parts, set-up charges).Incurred costs can be determined to a reasonable degree of absolute accuracy.

Performance costs include issues such as delivery per-formance, quality and requirements for service or mainte-nance. Performance costs are relative data. As long as it isvalid for relative comparison, it is less important that it bean absolute cost figure.

Policy factors are also relative. They encompass anyissue that your organization chooses to incorporate toreflect political or social policy directives. Issues such asrecycled content of materials, minority and women-owned

suppliers and political preference fall into this category.Typically a supplier or item either does or does not meetthe policy criterion. The factor is a yes / no factor, andestablishing a dollar value for it rests with the policy mak-ers within your organization.

Total Cost Factors for Inventory Materials:The following issues are typically included in the total

cost for items to be inventoried:Cost of Non-Delivery.You bear additional costs for a

supplier's failure to deliver on time. If the supplier deliversearly, you will pay for the goods sooner and carry theinventory longer. If the supplier delivers late, you wil l con-sume people's time to replan the materials schedule and/orexpedite the delivery. I f the lateness is chronic, you maycarry safety stock. Cost of non-delivery is a performancecost factor. As long as the measure is valid for relative com-parison, it does not have to reflect actual dollars incurred,which can be variable and would be difficult to calculatefor each situation.

A simple method to incorporate the cost of non-deliv-ery into total cost calculations is to use the non-deliveryperformance percentage as a price adder. For example, if Able Company delivers on time 85% of the time, thenthey are not on time 15% of the time. Multiply Able's

quoted price by 15% and add that amount to the baseprice as a cost factor for non-delivery. The better the deliv-ery performance, the lower the cost factor. Since each sup-plier bears the cost factor relevant to its own performance,it is a fair way to differentiate between suppliers based ontheir performance.

Cost of Non-Quality. The cost of non-qualityincludes the overhead expense of an incoming qualityinspection, a reject-materials stockroom, the administrativeexpense of a materials review and the material return. If your organization uses activity-based costing, then the cost

of quality may be an identified cost pool. In that case yourorganization will have a good idea what those costs actuallyare, and you can apply known numbers to the total cost of ownership based on the proportion of the total resourceconsumption that the item represents.

If you do not have actual cost numbers, you can usethe measure of percent defective items as a price adder.For example, if 8% of Baker's material is rejected, thenBaker's price is multiplied by 0.08 and that amount isadded to the base price to compensate for your costs of handling non-quality goods. The higher the supplier'squality, the lower the cost factor, and since each supplierbears the cost factor relevant to its own performance, it is afair way to differentiate between suppliers.

Cost of transportation. If you pay for freight, itshould be included in total cost. To determine transporta-tion costs, obtain the invoice amounts (either from thesupplier's or the carrier's invoices) for several typical ship-ments. Add these costs and divide the total cost by the

total number of units shipped. This wil l give you the trans-portation cost per unit.Cost of Inventory. Keeping inventory is expensive.

Money is consumed paying for it which could be spentelsewhere. Inventory consumes more money just sitting onthe shelf. The cost to carry inventory normally includesthe interest rate of money, insurance, taxes, space andobsolescence reserve. Most corporate inventory carryingcosts are based on these factors alone, and the numbers aretypically 20-30% per year.

Unfortunately, basing the cost of inventory on thosefactors alone misses other areas of cost which are less easyto calculate but very real. Additional areas of cost include

personnel (whose function is inventory management / movement, such as warehousers, or inventory controllers),an appropriate allocation of computer systems costs, stor-age and handling equipment (such as forklift trucks andracking) and material losses / rework due to handling dam-age or induced quality problems. If these additional costsare included, the cost of inventory grows to more thandouble the commonly used figures.

Inventory carrying cost becomes a significant factor inthe total cost of ownership when new items are beingadded or when choice of supplier will have different inven-tory implications (such as a choice between a domestic ver-sus an international supplier or between any two suppliers

with significantly different lead times).To include inventory costs into the total cost of own-

ership, determine your annual cost to carry inventory (per-centage). Divide that percentage by 52 to determine thecarrying cost per week. Multiply this number by the num-ber of weeks of inventory you keep on hand. This gives apercentage that can be used as a cost adder in the samemanner as other performance percentages. (Multiply theprice by the percentage and add the result into the totalcost.)

22 NPMA © 2002 National Property Management Association Volume 14, Issue 2 – 2002



NPMA 23Volume 14, Issue 2 – 2002 © 2002 National Property Management Association

Use-related costs. This category includes ease of use,effect on final output, ability to automate or any measur-able effect that the item would have on the process inwhich it is used. Time factors can be translated into totalcost factors by multiplying the difference in time betweenthe alternatives by the labor rate of the people involved.The resulting cost difference can be applied to the totalcost of ownership.

Lead time can be included as a total cost factor if youwant to reduce lead times or if they differ between suppli-ers. Lead time can be factored into total cost as a percent-per-week. Establish a value that reflects the degree of emphasis you want to place on reduction. Start with 1%per week of lead time and evaluate whether that is appro-priate by comparing its weight to the other factors in thetotal cost profile.

Credits and debits.To make a fair comparison of sup-pliers or items, both contributions and costs should beincluded. If a supplier offers something of value to you,

then the "cost" of that should be calculated and subtractedfrom the supplier's total cost of ownership calculations.Similarly, if one item offers an advantage over another,then that advantage should be credited.

An example. Figure 1 illustrates the total cost calcula-tions used to make a selection among three suppliers:Able, Baker and Charlie. The cost factors that the cus-tomer selected as relevant include delivery performance,quality, transportation, lead time and recycled content.The suppliers also offered prompt payment discountswhich were credited.

Putting it all together. Establishing a total cost of ownership process serves your organization in numerousways. The process of selecting the criteria to be includedwill force the organization to become clear about what itvalues. This is particularly true for inventory purchases. Bygiving everyone in the organization access to the process,people in other functions who have a vested interest in thesupply base will be free to state their concerns and defineappropriate ways to represent them. The process becomes avehicle for cross-functional education, and when donewith grace results in cross-functional support. It also lendsitself well to the establishment of supplier managementteams.

Many people in purchasing have experienced selectionof a supplier in which they knew that the lowest price sup-plier was not the best choice. Using total cost of ownershipas a means of supplier selection allows all considerations tobe balanced and gives purchasing the data to justify theselection to anyone in the organization who may challenge

the decision. If the criteria are collectively derived andinternally public, there will be little reason to argue withthe decision, even if one person’s favorite supplier was notselected. Using total cost of ownership data to select sup-pliers results in a clearer selection process.

Externally, using total cost data sends a powerful mes-sage to suppliers. Reviewing each supplier’s total cost fig-ures with them until they understand how they were calcu-lated sends the message that it is total performance thatcounts – not just price. Suppliers can see clearly why theyare (or are not) competitive. If they did not get the busi-

ness, they can also see what they have to doto improve, and more options are open to

them than just slashing prices at the expenseof performance. They can see how improvingperformance will have a direct effect on theircompetitive position.

TOTAL COST CALCULATIONS EXAMPLE

Factor Able Co Baker Co Charlie Co

Quoted Price $10.00 $11.50 $12.00

Transport +.09 +.07 0$/Qty (8.95/100) (7.00/100)

Inventory +1.20 +1.04 [email protected]%/ wk (8 weeks) (6 weeks) (1 week)

Lead Time +2.00 +2.07 +1.44@2%/ wk (10 weeks) (9 weeks) (6 weeks)

Quality +1.30 +.92 0

%Reject (13%Reject) (8%Reject) (No rejects)

On-Time Del +1.50 +1.27 +1.201 - %OT (85%OT) (89%OT) (90%OT)

Discounts - .20 - .06 - .12Cash (2%10 Net 30) (.5%10 Net 30) (1%10 Net 30)

Cost SaveReuse Con -1.00

______ ______ ______ Total Cost $15.89 $16.81 $13.70

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