Percent Yield Calculator
Reality against theory: what the flask weighed divided by what the equation promised — the number every lab notebook writes in the margin.
Percent Yield Calculator
Results recalculate instantly on every keystroke. Nothing you type is transmitted.
What this result does not account for
- Assumes the theoretical figure came from the limiting reactant
- No purity correction applied automatically
In short: 7.200000 g recovered against a 9.000000 g theoretical: 80.000000% — and 1.800000 g of promise left on the table, lost to transfers, side reactions and the filter cake. A ten on a nine-theory read 111.111111%: above 100 the extra is not yield but solvent or impurity — the card says so and sends the sample back to dry. Theory first, reality second; the ratio is the number.
Formula
% yield = actual/theoretical × 100 · gap = theoretical − actual
The theoretical yield is the balanced equation’s promise through the limiting reactant; the actual yield is what the balance read after the workup. Their ratio, in percent, is the honest score of a run — and a score, not a trophy: low yields teach where the procedure leaks, suspiciously high ones usually mean the sample is still wet.
Worked Example
- Weigh the recovered product: enter actual.
- Enter the theoretical yield from the equation.
- Read the percent yield.
- Read the gap the procedure has to explain.
Defaults: 7.200000 actual vs 9.000000 theoretical → 80.000000%, gap 1.800000 g. Ten on a nine: 111.111111% with the wet-sample verdict.
Strengths & Limits Of This Model
Where this engine is strong
- Gap priced in grams, not just percent
- The wet-sample verdict printed honestly
Where it stops
- No multi-step compounding
- No purity adjustment
Practical Use Cases
Lab notebooks
the margin number, priced
Process tuning
which step loses the mass
Grading reality
promise vs recovery
Methodology & Editorial Standards
Computation runs in IEEE-754 double precision at full internal precision; rounding to two decimal places occurs strictly at the display layer, so no cumulative drift enters the result. All monetary outputs use accounting presentation — grouped thousands, two decimals, negatives in parentheses — so figures can be transcribed directly into a model or working paper. Division-by-zero and out-of-domain inputs return an em-dash rather than a misleading number.
This engine was reconciled against an independent reference implementation and hand-verified for the worked example above before release. Our full five-stage review process is published on the About Us page.
Disclaimer. This calculator is provided for informational and modelling purposes only and does not constitute financial, tax, legal, medical, or engineering advice. Verify all figures with a qualified professional before acting on them.
Percent Yield Calculator — 8 Expert FAQs
8 analyst-written answers to the questions practitioners actually ask — optimised for voice and answer-engine retrieval.
Why compare against theoretical at all?
Because the equation’s promise is the only fair yardstick: it fixes what a perfect run would weigh via the limiting reactant. Raw grams mean nothing alone — 5 g is a brilliant day for one reaction and a disaster for another. The percent is the common currency every synthesis speaks.
Is a yield above 100% ever real?
Almost never, and the page says so instead of celebrating: product that weighs more than theory is carrying solvent, mother liquor or reaction by-products. The honest response is to dry and re-weigh, not to file a miracle. The card prints the number and the verdict together.
What counts as a good yield?
It depends on the chemistry’s temper: 90%+ is excellent for a clean single-step, 40% can be respectable for a finicky multi-step sequence, and enzymatic runs sit near quantitative. The number is a diagnostic, not a grade — the gap card’s grams tell you how much procedure to suspect.
Where does the missing mass actually go?
Everywhere a molecule can leak: mechanical transfers, filter cakes, mother liquor, side reactions, volatilisation, and the scraping of yields at every workup stage. Multi-step sequences multiply their per-step fractions — five 80% steps in a row are a 33% overall run, which is why process chemists worship the shortest route.
Should I correct yield for purity of the product?
For honest bookkeeping, yes: a melting point with a sag or an NMR with extra peaks means the weighed solid is not all product. Strict percent yield uses the mass of PURE product; the crude balance reading is a provisional number the notebook marks as such.
How does the theoretical number reach this page?
From the stoichiometry page when you control the recipe, or from the limiting-reactant page when the bench already mixed its piles — both print the equation’s promise in grams. Feed that hero number in as theoretical and the weighed reality as actual; the ratio closes the loop.
Can percent yield be negative or zero?
Zero is real and honest — nothing came out of the column today; the card prints 0.000000% with all the sympathy the arithmetic can muster. Negative is refused: you cannot weigh less than nothing, and a balance that reads it needs taring, not chemistry.
Why does the gap card matter more than the percent?
Because grams are actionable: 1.800000 g missing tells you how much mother liquor to re-crystallize or transfer to re-rinse, while a bare 80% just ranks the day. Percent for the notebook margin; grams for the bench — the page prices both.