Operating Cost (OPEX) Dashboard · Green Chemistry Economics
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Operating Cost dashboard.

Model the cost per unit of a real manufacturing process from materials, labour and overhead, watch the numbers update live as you edit, and see how batch scale changes the economics. Toggle on a selling-price model if you want to explore margin and pricing too. Prefer an itemised, line-by-line cost sheet instead? Try the OPEX calculator.

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What is OPEX — and why does it matter?

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Operating Cost (OPEX) is the total recurring cost of producing one unit of product: the sum of materials, labour and overhead. Where Raw Material Cost (RMC) isolates the materials line, OPEX rolls all three cost pillars into a single per-unit figure, and lets you see how they trade off against each other and against production scale.

GoalUnderstand which cost pillar dominates a process, and how much scrap, batch size, and material choice each move the final cost per unit.
WhyThe same process can look economically marginal at lab scale and highly viable at plant scale, purely because fixed overhead is spread across more units. Conflating "expensive to make" with "expensive at this scale" is a common error when assessing whether a greener route is commercially feasible.
HowReduce scrap and rework, recover and reuse materials, increase batch size to dilute fixed overhead, and weigh any cost premium of a safer or more sustainable material against the externalities it avoids.

The formula

$$\text{OPEX} = C_{\text{materials}} + C_{\text{labour}} + C_{\text{overhead}}$$
SymbolTermUnits
$C_{\text{materials}}$$\sum_i q_i c_i (1+s_i)$ — quantity $q_i$ × unit cost $c_i$ of material $i$, inflated by its scrap fraction $s_i$currency / unit
$C_{\text{labour}}$$h\,r\,(1+b)$ — labour hours $h$ per unit × rate $r$, inflated by benefits multiplier $b$currency / unit
$C_{\text{overhead}}$$\dfrac{F}{N} + v$ — fixed monthly overhead $F$ spread across batch size $N$, plus variable overhead $v$ per unitcurrency / unit

Scrap cost is shown separately in the dashboard: it is the financial expression of the same waste an E-factor measures in mass, reducing it lowers cost and environmental burden together.

OPEX and other economic metrics

OPEX is one of several economic lenses in the toolkit alongside Raw Material Cost (RMC), Cost Effectiveness, and Capital Efficiency. RMC is the materials line item inside OPEX; OPEX adds labour and overhead to give the full recurring cost of production.

MetricWhat it measuresStage
RMCTotal raw material cost per unit mass of productMaterials
OPEXOngoing operating cost per unit product, including materials, labour, and overheadOperations
Cost Effectiveness (CE)Value or output achieved relative to total cost incurredOperations
Capital Efficiency (CapE)Return generated relative to capital invested in plant and equipmentInvestment

Strengths and limitations

Strengths

  • Combines all three major recurring cost pillars into one comparable per-unit figure
  • Directly shows the economies-of-scale effect of batch size on fixed overhead
  • Isolates scrap cost, connecting a financial figure to a waste metric students already know
  • The optional selling-price toggle lets pricing be explored without treating it as the tool's core purpose

Limitations

  • Excludes one-off capital expenditure (equipment, plant) — see Capital Efficiency for that lens
  • Labour and overhead figures are process-level estimates, not activity-based costing
  • Prices and rates change over time and by region; results should be dated and sourced
  • Assumes materials/labour cost per unit stays constant across scale, only overhead is diluted
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Process details

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03 Cost dashboard

Everything below recalculates live as you type — no calculate button. The right-hand panel stays in view while you edit inputs on the left.

Materials (BOM)

Enter each material per unit of product: reagents, solvents, catalysts, components, packaging. Scrap rate inflates the line cost to reflect real-world loss/rework.

Material name Category Qty / unit Unit cost (£) Scrap (%) Line cost (£)

Labour

Direct labour time and cost to produce one unit.

Overhead & batch

Fixed overhead is spread across the batch; variable overhead is charged per unit regardless of scale.

Model selling price & margin Optional — for students exploring pricing on top of cost
OPEX per unit
£—
materials + labour + overhead
Materials
£—
—
Labour
£—
—
Overhead
£—
—
Batch total cost
£—
per month, at entered batch size
Scrap cost / unit
£—
the "hidden cost" of waste

Cost by pillar

Economies of scale — OPEX per unit vs batch size

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Detailed breakdown & interpretation

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Line itemCategoryCost (£/unit)% of OPEXVisual
Enter materials, labour and overhead above to see the breakdown.

Interpretation

Enter materials, labour and overhead above to generate an interpretation.
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Save & load sessions

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Sessions are stored in your browser only. No data leaves your device.

No saved sessions yet.
06

Export

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Export your OPEX model as a PDF report or CSV data file. PDF opens in a new tab and uses your browser's print function. Selling-price figures are only included if the toggle above is on.

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Where can I read more?

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  1. P. T. Anastas and J. C. Warner, Green Chemistry: Theory and Practice, Oxford University Press, 1998.
  2. M. Butters et al., Chem. Rev., 2006, 106, 3002-3027. DOI. Critical Assessment of Pharmaceutical Processes: A Rationale for Changing the Synthetic Route.
  3. C. Jiménez-González et al., Org. Process Res. Dev., 2011, 15, 912-917. DOI. Using the Right Green Yardstick: Why Process Mass Intensity is Used in the Pharmaceutical Industry to Drive More Sustainable Processes.
  4. R. A. Sheldon, Green Chem., 2007, 9, 1273-1283. DOI. E-factor across sectors; economic context for green metrics.
  5. J. Fortunak et al., Raising the Technological Level: The Scope for API, Excipients, and Biologicals Manufacture in Africa, in Making Medicines in Africa, Palgrave Macmillan, London, 2017. DOI. Rule-of-thumb share of raw materials in manufacturing cost.
  6. D. T. Kearney and B. J. Fenech-Salerno, teaching materials, DodecaGreen Project, Imperial College London, 2026. Materials/labour/overhead cost roll-up structure adapted for green chemistry economics teaching.
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Contributors

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Roles follow the CRediT taxonomy, adapted for educational software. Hover a contributor's name for a summary, or a column header for the role definition.

Contributor

© 2025– DodecaGreen Project. All rights reserved. · Last updated: 14/08/2026

This portal was built with the assistance of a large language model (Claude, Anthropic), which was used to generate and refine code, articulate and structure contributed ideas within the defined page format, and support iterative design decisions. All scientific content, conceptual frameworks, pedagogical choices, and final outputs were directed, reviewed, and verified by the contributors listed above.

Whilst every effort has been taken to ensure accuracy, mistakes can happen. If you notice something that doesn't look quite right, kindly reach out to the DodecaGreen team via the Contact page.

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How do I cite this page?

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If you use this tool in teaching or published work, please cite the DodecaGreen portal as the source.

Reference
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