Manufacturing should-cost model: a buyer's template for supplier quotes

TL;DR

• A should-cost model independently rebuilds a factory selling price from the part, route, and volume instead of starting with the supplier quote, consistent with DFMA's method.
• Model material, setup, cycle, labor, tooling, yield, quality, overhead, and profit as separate sourced rows, then test documented drivers one at a time.
• Treat the result as a hypothesis, not the supplier's books, landed cost, customs value, technical approval, or proof that a quote is high or low.
• Use the workbook to identify the next driver to clarify, then move the reconciled quote into comparison, readiness, or a Tandom sourcing project.

Choose the right use case before building the model

Build a detailed should-cost only when the decision can justify the work. It is most useful when a recurring custom part has a wide quote spread, limited competition, a proposed increase, or a design and volume tradeoff that past prices cannot explain.

FAR 15.404-1 separates price analysis from analysis of individual cost elements and profit. Those federal rules do not govern private industrial purchases. The distinction is still useful: compare market prices when comparable evidence is enough; build the cost when price evidence cannot explain the decision.

Freeze one technical and commercial baseline

The model and supplier quote must describe the same thing. Record each field below before a rate or percentage enters the workbook.

If the quote uses another revision, quantity, route, or quality scope, request a controlled clarification or requote. Do not repair a technical mismatch with a spreadsheet premium. The quote comparison guide shows how to preserve quoted values and normalize supported commercial differences.

Build the model from physical cost drivers

Start with material and the plausible operation sequence. Add commercial percentages only after direct inputs are visible. The DFMA manufacturing-cost guide separates material, machine time, labor, setup, tooling, secondary operations, and yield. It also warns against double-counting labor or overhead already included in a burdened rate.

Model material from input, not finished weight

Record the grade, stock form, gross input, purchased components, date-stamped rate, and supported scrap recovery. A machined part can begin with more material than remains in the finished component.

Route every manufacturing operation

Put one operation on each row. Separate setup from per-attempt cycle. Separate unattended machine time from attended labor when the resource model supports it. Name outside processing, inspection, testing, and packaging instead of hiding them in overhead.

Apply loss where it occurs

Yield changes the attempted units needed for one good unit. Apply supported loss at the operation where it occurs. A late reject carries more accumulated material and variable operation cost than an early reject. Keep fixed setup cash outside the yield cascade and divide its total once by the final good-unit release quantity. If only cumulative yield is available, disclose and test that shortcut.

Separate recurring tool wear from one-time cash

Allocate recurring wear over demonstrated good-unit life. Keep dedicated tooling and NRE visible by payment milestone. This workbook does not amortize one-time cash into repeat unit economics; each Volume row adds the full one-time amount to first-order cash instead.

Add overhead once

Write what machine and labor rates include. A burdened machine rate may already cover depreciation, utilities, maintenance, floor space, and indirect support. Adding the same items again inflates the model.

Choose markup or sales margin

A sustainable supplier price includes profit, but the convention must be explicit. A 20% markup on a 100 cost base produces 120. A 20% sales margin produces 125 because cost is 80% of price.

Material input cost per attempt
= input quantity x dated unit rate
  - supported recoverable scrap quantity x recovery fraction x scrap unit value

Total fixed setup cash per release
= sum of setup hours per release x setup resource rate across operations

Fixed setup cost per final good unit
= total fixed setup cash / final good-unit release quantity

Operation cost per attempt excluding setup
= cycle hours x machine rate
  + attended labor hours x labor rate
  + operation consumables

Sequential cumulative cost after operation n
= (prior cumulative cost + variable operation cost per attempt)
  / operation yield + downstream outside processing + rework
  fixed setup is not included in this yield cascade

Price using profit markup
= supported cost base x (1 + markup rate)

Price using sales margin
= supported cost base / (1 - sales margin)

Quote gap
= normalized quoted factory price - modeled factory selling price

Formal government should-cost reviews are broader than this workbook. FAR 15.407-4 can involve contracting, pricing, audit, and engineering specialists. Use that as a reminder to involve the right buyer functions, not as a rule governing private purchasing.

Make uncertainty visible and reviewable

A defensible model explains what is known, estimated, and open. The goal is not more decimal places. It is to identify the assumptions that deserve evidence.

Test one driver at a time

Build low, base, and high cases from supported alternatives or dated inputs. Change one driver at a time and treat the lowest and highest outputs as a tested envelope rather than a combined forecast. Do not apply an arbitrary percentage to every row. The GAO Cost Estimating and Assessment Guide recommends changing one factor at a time, documenting the source of variation, and identifying which assumptions move the result most.

1. Rank cost elements by their share of the modeled total.
2. Identify the uncertain input behind each large element.
3. Set low and high values from traceable evidence.
4. Recalculate one input at a time while holding others fixed.
5. Record the output change and the next evidence action.

Normalize currency before using the workbook

Choose one model currency and convert every material, resource, tooling, outside-process, quality, and packaging input before pasting it into a model-currency field. Retain the original currency, conversion direction, source, and observation date in the source columns or evidence log. The Federal Reserve H.10 release is one public source for bilateral rates, but it does not cover every company policy or currency need. This workbook intentionally has no global FX multiplier because one factor cannot safely normalize mixed source currencies.

Copy this ten-sheet should-cost workbook

Create tabs with these exact names and paste the matching section into cell A1: Baseline, Material, Routing, Tooling, Quality, Volume, Quote_Gap, Sensitivity, Evidence_Log, and Summary. The executable formulas use those tab names and will break if they are changed.

Paste all ten sheets before entering data. Fill blank input cells and the documented low and high cases; do not overwrite columns that begin with =. Enter percentages as decimals such as 0.12 for 12 percent. Protect formula cells, validate evidence status, pre-normalize cost inputs into the Baseline model currency, retain source currency and dates, and assign every decision-relevant Open row.

1. Baseline (tab name: Baseline)

2. Material (tab name: Material)

3. Routing (tab name: Routing)

4. Tooling and NRE (tab name: Tooling)

5. Quality and packaging (tab name: Quality)

6. Volume scenarios (tab name: Volume)

7. Supplier quote gap (tab name: Quote_Gap)

8. Sensitivity (tab name: Sensitivity)

9. Evidence log (tab name: Evidence_Log)

10. Summary (tab name: Summary)

The summary shows first-order cash and repeat-order economics separately. It does not add freight, duty, tariffs, inventory, warranty, or downtime. Its lowest and highest tested values are an envelope of individual one-factor tests, not a combined forecast. Continue with the quote-comparison and landed-cost workflow after the factory-price boundary is reconciled.

Worked example: one bracket, one explainable model

A US industrial buyer is evaluating machined bracket BRKT-042 Rev C. The repeat release is Q good units. The model and quote include the same material, finish, inspection, records, packaging, and named factory handoff. International freight and import costs are excluded.

Map the route and evidence

Roll up the good-unit cost

M = material input cost after supported scrap recovery
C0 = M
S = total fixed setup cash across operations
Qrelease = final good-unit release quantity
Rn = cycle machine labor and consumables for operation n
Yn = supported yield at operation n
Dn = downstream outside processing and rework after operation n
T = recurring tool wear per good unit
Q = inspection and packaging per good unit
H = supported factory overhead applied once to its named base
p = supplier profit markup on the stated cost base

C1 = (C0 + R1) / Y1 + D1
C2 = (C1 + R2) / Y2 + D2
Continue once per operation so later loss carries every upstream cost
Factory cost per good unit = final Cn + (S / Qrelease) + T + Q + H
Modeled factory selling price = factory cost per good unit x (1 + p)
Absolute quote gap = quoted factory price - modeled factory selling price

If profit is expressed as sales margin m instead:
Modeled factory selling price = factory cost per good unit / (1 - m)

Each low or high test changes one documented material, cycle, yield, rate, or quantity input while holding every other base input fixed. The lowest and highest outputs form a one-factor envelope. They are not the result of combining every favorable or unfavorable input.

Turn the quote gap into questions

• If material is higher, ask about stock form, purchase lot, input weight, yield, and preparation.
• If conversion is higher, reconcile route, equipment, setup, cycle, attendance, rate inclusions, and subcontracting.
• If the quote is lower, confirm the same revision, material, finish, inspection, records, and pack.
• If one-time cash explains the gap, keep it separate from repeat-order economics.
• If no row explains the gap, preserve it as unresolved instead of forcing overhead or profit to fit.

Stop before customs value

The model is not an import declaration. Under 19 CFR 152.103, transaction value starts with the price actually paid or payable and can require specified additions. The importer and its broker or qualified adviser must review the actual transaction facts.

Common pitfalls and what they break

Glossary

Should-cost

A buyer's independent estimate of plausible cost or selling price under explicit assumptions.

Clean-sheet costing

A bottom-up estimate built from current physical and process drivers.

Price analysis

Evaluation of offered price without evaluating every separate cost element.

Cost analysis

Evaluation of separate cost elements and profit behind a proposed price.

Technical baseline

The controlled part, revision, material, process, quality, and other requirements.

Manufacturing route

The ordered operations, resources, sites, outside processes, and controls.

Cycle time

Processing time attributed to one attempted unit for a named operation.

Setup time

Time required to prepare a resource for a stated batch or run.

Machine rate

Cost per unit of machine time with its inclusions stated.

Burdened rate

A rate that includes named indirect costs in addition to direct resource cost.

Yield

Good output divided by attempted input on a defined basis.

Scrap recovery

Supported value recovered from material that does not remain in the good part.

NRE

Non-recurring engineering, programming, development, or validation work.

Markup

Profit divided by its cost base.

Sales margin

Profit divided by selling price.

Factory-price boundary

The production, quality, packaging, overhead, profit, and handoff layers included in price.

FAQ

Practical answers for US industrial buyers building and reviewing a manufacturing should-cost model.