E‑factor calculator.
Calculate the Environmental Factor of any chemical process from the actual masses of inputs and isolated product.
What is E-factor — and why does it matter?
The E-factor (Environmental Factor), introduced by Roger Sheldon in 1992, is a direct experimental measure of how much waste a chemical process generates per unit of desired product. Unlike atom economy, E-factor captures everything that actually happens in the lab, including solvents used, reagents not incorporated, workup waste, and by-products, making it a powerful tool for real-world process evaluation.
The formula
| Symbol | Term | Units |
|---|---|---|
| \(E\) | E-factor (Environmental Factor) | dimensionless (kg kg−1); ideal value = 0 |
| \(m_{\text{waste}}\) | Total mass of all process outputs except the desired product (side-products, spent solvent, wash liquors, excess reagents, drying agents) | kg (or g) |
| \(m_{\text{product}}\) | Mass of isolated desired product | kg (or g) |
"Waste" is everything that is not the desired product: unreacted starting materials, by-products, solvents not recovered, spent catalysts, wash liquors, and any auxiliary materials. A lower E-factor is always better. Recovered and recycled materials reduce the waste total.
Typical E-factor by industry sector
| Industry segment | Product tonnage (p/a) | E-Factor (kg waste/kg product) |
|---|---|---|
| Oil refining | 106–108 | < 0.1 |
| Bulk chemicals | 104–106 | < 1–5 |
| Fine chemicals | 102–104 | 5–50 |
| Pharmaceuticals | 10–103 | 25–>100 |
Adapted from R. A. Sheldon, "The E factor at 30: a passion for pollution prevention", Green Chem., 2023, 25, 1704–1728.
Strengths and limitations
Strengths
- Experimental: captures real-world waste including solvents and workup
- Simple to calculate from lab records; no molecular weights needed
- Directly comparable across processes, scales, and industries
- Can account for solvent/catalyst recovery — rewards circular approaches
- Widely adopted across industry and pharmaceutical roundtables
Limitations
- Requires experimental data so cannot be calculated at the design stage
- Treats all waste equally: 1 kg of water = 1 kg of toxic solvent
- Does not capture energy consumption, toxicity, or life-cycle impacts
- Dependent on scale and process efficiency; hard to compare across scales
- Can be "gamed" by excluding or mis-categorising waste streams
E-factor in context: complementary green metrics
| Metric | What it measures | Stage |
|---|---|---|
| Atom Economy (AE) | Theoretical fraction of reactant mass in desired product (from equation) | Design |
| % Yield | Fraction of theoretical product actually isolated | Experimental |
| E-factor | Mass of all waste per mass of product (all inputs, real scale) | Experimental |
| PMI (Process Mass Intensity) | Total mass of all inputs per mass of product; PMI = E-factor + 1 | Experimental |
| RME (Reaction Mass Efficiency) | AE × yield × stoichiometric factor — combined practical efficiency | Both |
Experiment details
Input materials
Enter all materials used in the process: reagents, solvents, catalysts, and workup/purification materials. If a solvent or catalyst is recovered and recycled, enter that mass in "Recovered" — it is subtracted from the waste total. Do not enter the product here.
| Material name | Category | Mass used (g) | Recovered (g) | Net waste (g) |
|---|
Desired product(s)
Enter the mass of each desired product actually isolated (not theoretical yield). If your process produces multiple valuable products, add each one — their combined mass forms the denominator of the E-factor.
| Product name | Mass isolated (g) |
|---|
Results
Waste by material category
Product vs. waste mass balance
Detailed breakdown & interpretation
| Material | Category | Mass used (g) | Recovered (g) | Net waste (g) | % of waste | Visual |
|---|---|---|---|---|---|---|
| Enter input materials and product above to see breakdown. | ||||||
Interpretation
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Export
Export your E-factor calculation as a PDF report or CSV data file. PDF opens in a new tab and uses your browser's print function. CSV downloads directly.
Where can I read more?
References are sorted alphabetically by first author.
- ACS Green Chemistry Institute. Green Chemistry Resources & Solvent Selection Guide. acs.org/greenchemistry. — Pharmaceutical Roundtable solvent-selection scoring and PMI benchmarking data.
- P. T. Anastas and J. C. Warner, Green Chemistry: Theory and Practice, Oxford University Press, 1998. ISBN 978-0-19-850698-0. — Original statement of the 12 Principles; frames waste prevention as Principle 1.
- D. J. C. Constable, A. D. Curzons and V. L. Cunningham, Metrics to 'green' chemistry — which are the best?, Green Chem., 2002, 4, 521–527. DOI. — A good further reference for the strengths and limitations of E-factor and related green chemistry metrics.
- C. Jiménez-González et al., Org. Process Res. Dev., 2011, 15, 912–917. DOI. — Defines PMI; shows solvents account for ~85% of process mass.
- R. A. Sheldon, Organic Synthesis — Past, Present, and Future, Chem. Ind., 1992, 903–906. — The original paper introducing the E-factor.
- R. A. Sheldon, Green Chem., 2007, 9, 1273–1283. DOI. — E-factor fifteen years on: typical values across chemical sectors.
- R. A. Sheldon, The E factor at 30: a passion for pollution prevention, Green Chem., 2023, 25, 1704–1728. DOI. — E-factor 30-year retrospective; source of Table 1 industry-sector benchmarks.
Contributors
Roles follow the CRediT taxonomy (Contributor Roles Taxonomy), adapted for educational software. Hover a contributor's name for a summary, or a column header for the definition of that role.
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