product molar mass ÷ Σ reactant molar masses × 100 — green-chemistry atom efficiency, with how it differs from percent yield — browser-only
- Runs locally
- Category Calculator
- Best for Getting a realistic range before a purchase, plan, workout, or schedule decision.
One per line. Include the product’s reactants — commas also work.
About this number
A middling atom economy means a fair share of the reactant mass leaves as by-product. Substitution and elimination reactions sit here: making chloromethane from methane loses HCl, so the wanted product carries only part of the mass.
Atom economy is theoretical and comes from the balanced equation; percent yield is experimental and measures what you actually isolated. A reaction can score 100% on one and 60% on the other.
atom economy = product molar mass ÷ Σ(reactant molar masses) × 100
What this tool does
Free atom economy calculator for green chemistry, A-level and undergraduate organic chemistry. Atom economy (atom efficiency) measures how much of the reactant mass ends up in the product you actually want: atom economy = molar mass of the desired product ÷ the sum of the molar masses of every reactant × 100. Enter the product's molar mass and the molar mass of each reactant on its own line, and the tool sums the reactants and returns the percentage. A high figure means a lean reaction that throws away little as by-product, which is principle 2 of the 12 Principles of Green Chemistry. Atom economy is theoretical, fixed by the balanced equation, so it differs from percent yield, which measures what you isolated in the flask. Addition reactions reach 100%; substitution and elimination lose mass to by-products. Everything runs in your browser with one-click copy and a shareable link that reopens the same numbers. 100% client-side, nothing uploaded.
Tool details
- Input
- Text + Numbers
- The page exposes text boxes, numeric controls, file pickers, or structured inputs depending on the tool.
- Output
- Live result + Copy + Preview
- The result area focuses on usable output, with copy, download, or preview actions when supported.
- Privacy
- Browser-side processing
- The main tool logic does not call an external API, so inputs normally stay in the current tab.
- Save / share
- Shareable URL state
- Key settings are encoded in the URL so another person can reopen the same setup.
- Performance budget
- Initial JS <= 9 KB
- No WASM budget is declared, keeping the tool quick to open on mobile.
- Best fit
- Calculator · Student
- Category and role tags drive related tools, internal links, and quick fit checks.
How to use
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1. Input
Paste or drop your content into the tool panel.
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2. Process
Click the button. All processing is local in your browser.
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3. Copy / Download
Copy the result or download to disk in one click.
How Atom Economy Calculator fits into your work
Use it for fast estimates, comparisons, and planning numbers before you make the final call.
Calculation jobs
- Getting a realistic range before a purchase, plan, workout, or schedule decision.
- Comparing scenarios by changing one input at a time.
- Turning rough assumptions into a number you can discuss.
Calculation checks
- Double-check units, dates, rates, and rounding assumptions.
- Treat health, finance, tax, and legal outputs as planning aids, not professional advice.
- Save the inputs that produced an important result so you can reproduce it later.
Good next steps
These links move the current task into a more complete workflow.
- 1 Molar Mass Calculator Type any chemical formula — get molar mass, a per-element mass-percent table, and mass↔mole conversion. IUPAC weights, browser-only. Open
- 2 Percent Yield Calculator actual ÷ theoretical × 100 — solve for percent, actual or theoretical yield, grams or moles, with a plain-English read on why it is below or above 100% — browser-only Open
- 3 Molarity Calculator Molar concentration c = n / V — solve any one of moles, volume, concentration, or go straight from grams + molar mass — browser-only Open
Real-world use cases
Score a green-chemistry exam question on the spot
An A-level or first-year exam asks for the atom economy of making a named product. Look up or compute the molar masses, type the product mass up top and each reactant on its own line, and read the percentage straight off. The tool also restates the formula and explains why an addition reaction lands at 100% while a substitution does not, so you can write the reasoning, not just the number, in your answer.
Compare two synthetic routes before the lab
You can make the same target by substitution or by addition. Enter the product and reactant molar masses for each route in turn and compare the two percentages. The greener route is the one that keeps more reactant mass in the product, and seeing 100% next to 55% makes the choice obvious before you have wasted a single reagent at the bench.
Build a teaching example that contrasts atom economy and yield
Preparing a lesson, you want a reaction with a high yield but a poor atom economy to show students the two are not the same thing. Plug in the masses, point at the 100% atom economy of the addition example and the lower figure of the substitution example, and the difference between a theoretical formula property and an experimental measurement becomes concrete instead of abstract.
Sanity-check an industrial route's waste profile
Reading a process chemistry paper that quotes an atom economy, you want to verify it. Sum the reactant molar masses from the scheme, enter the product mass, and confirm the published figure. If your number lands above 100%, a reactant such as water or an acid was left out of the balanced equation, which the tool flags so you know to look for the missing species.
Common pitfalls
Leaving a reactant off the list. Water, hydrogen, a halogen or an acid is easy to forget, and dropping it shrinks the denominator so the atom economy looks higher than it is — often above 100%, which the tool flags as impossible. List every species on the left of the balanced equation.
Confusing atom economy with percent yield. Atom economy is a theoretical property of the balanced equation; yield is what you actually isolated. A reaction with 100% atom economy can still give a 50% yield. Use this tool for the formula figure and the percent-yield calculator for the experimental one.
Forgetting to balance the equation first. The molar masses you sum must match the balanced stoichiometry, including coefficients. Two moles of a reactant means counting its molar mass twice in the sum. If the equation is unbalanced, every atom-economy number that follows is wrong.
Privacy
Every calculation — summing the reactant molar masses, dividing by the product mass, and the percentage — is plain JavaScript that runs in your browser tab. No molar mass or reaction you enter is uploaded, logged, or sent to any server, and there is no external API call. The one caveat: the shareable link encodes the product mass and reactant list in the query string, so a share link pasted into chat records those numbers in the recipient server's access log. Molar masses are not sensitive, but if you'd rather not, use the copy button instead of sharing the URL.
FAQ
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