Percent Yield Calculator
Example 1
A student synthesises aspirin in the laboratory, starting with 2.00 g of salicylic acid (MW = 138.12 g/mol) and excess acetic anhydride. After purification, the student isolates 2.40 g of pure aspirin (MW = 180.16 g/mol).
Solution
Percent yield is defined as the ratio of actual yield to theoretical yield:
The reaction is 1:1 between salicylic acid and aspirin. Moles of salicylic acid = 2.00 g / 138.12 g/mol = 0.01448 mol. Since the stoichiometry is 1:1, the theoretical yield of aspirin is also 0.01448 mol, which corresponds to 0.01448 mol × 180.16 g/mol = 2.61 g.
Substituting the actual and theoretical yields into the formula:
Answer
91.9% yield
This is a good yield for a student preparation. Losses may occur during recrystallisation and transfer between vessels.
This is a good yield for a student preparation. Losses may occur during recrystallisation and transfer between vessels.
Source: Vogel's Textbook of Quantitative Chemical Analysis
Example 2
A chemist reacts 3.00 g of acetic acid (MW = 60.05 g/mol) with 2.50 g of ethanol (MW = 46.07 g/mol) to produce ethyl acetate (MW = 88.11 g/mol). After the reaction and purification, 2.85 g of ethyl acetate is obtained.
Solution
Percent yield is the ratio of actual to theoretical yield:
The reaction is 1:1 between acetic acid and ethanol. First, identify the limiting reagent by comparing moles. Acetic acid: 3.00 g / 60.05 g/mol = 0.0500 mol. Ethanol: 2.50 g / 46.07 g/mol = 0.0543 mol. Acetic acid has fewer moles and is the limiting reagent.
The theoretical yield of ethyl acetate equals the moles of limiting reagent: 0.0500 mol × 88.11 g/mol = 4.41 g.
Substituting the values into the percent yield formula:
Answer
64.6% yield
Esterification is an equilibrium reaction, and the moderate yield reflects incomplete conversion plus purification losses. Using a Dean-Stark trap to remove water could improve the yield.
Esterification is an equilibrium reaction, and the moderate yield reflects incomplete conversion plus purification losses. Using a Dean-Stark trap to remove water could improve the yield.
Example 3
A pharmaceutical company runs a three-step synthesis to produce a drug intermediate. Step 1 yield: 85%, step 2 yield: 72%, step 3 yield: 91%. Calculate the overall percent yield for the sequence.
Solution
Overall yield for a multi-step synthesis is the product of each step yield expressed as a decimal:
Substituting the individual step yields:
Converting to percentage:
Answer
55.7% overall yield
Across three steps, each step compounds losses, making the overall yield significantly lower than any individual step.
Across three steps, each step compounds losses, making the overall yield significantly lower than any individual step.
Source: IUPAC Gold Book - Yield
Example 4
A student reacts 5.00 g of copper(II) sulfate pentahydrate (MW = 249.68 g/mol) with excess zinc metal to produce copper metal. The reaction also produces zinc sulfate as a byproduct. After filtering and drying, the student obtains 1.52 g of copper. Calculate the percent yield.
Solution
Percent yield is defined as the ratio of actual yield to theoretical yield:
The balanced equation shows a 1:1 mole ratio between copper sulfate and copper:
Moles of CuSO₄·5H₂O = 5.00 g / 249.68 g/mol = 0.0200 mol. Theoretical yield of copper = 0.0200 mol × 63.55 g/mol = 1.27 g.
Substituting the actual and theoretical yields into the formula:
Answer
119.7% yield
This exceeds 100%, which indicates the product is not pure – it likely contains unreacted zinc or absorbed water. The student should purify the product further before weighing.
This exceeds 100%, which indicates the product is not pure – it likely contains unreacted zinc or absorbed water. The student should purify the product further before weighing.
Source: IUPAC Gold Book – Yield
Published:
Updated:
References
- [1]Pearson, Vogel's Textbook of Quantitative Chemical Analysis, 2000.
- [2]IUPAC, IUPAC Gold Book - Yield. https://goldbook.iupac.org/terms/view/Y06762
- [3]American Chemical Society, ACS Green Chemistry Institute - Metrics. https://www.acs.org/greenchemistry/research-tools/metrics.html
Glossary
- Percent yield – The ratio of the actual yield to the theoretical yield multiplied by 100, expressed as a percentage. It measures the efficiency of a chemical reaction and is a standard metric in synthetic chemistry.
- Theoretical yield – The maximum amount of product that can be obtained from a chemical reaction, calculated from stoichiometry assuming complete conversion of the limiting reactant with no losses. It represents the ideal outcome.
- Actual yield – The amount of product actually obtained from a chemical reaction, measured experimentally after purification. The actual yield is always less than or equal to the theoretical yield due to losses and side reactions.
- Limiting reactant – The reactant that is completely consumed first in a chemical reaction, thereby determining the maximum amount of product that can be formed. All other reactants are present in excess.
- Excess reactant – A reactant that remains after the limiting reactant has been completely consumed. The amount of excess reactant is calculated by subtracting the consumed amount from the initial amount.
- Stoichiometry – The quantitative relationship between reactants and products in a chemical reaction, based on the balanced chemical equation. Stoichiometric calculations use mole ratios derived from the coefficients in the balanced equation.
- Atom economy – A measure of the efficiency of a chemical reaction calculated as the molecular weight of the desired product divided by the sum of the molecular weights of all reactants, expressed as a percentage. It reflects the green chemistry principle of waste minimisation.
- Side reaction – An unintended chemical reaction that consumes starting materials or intermediates to produce byproducts instead of the desired product. Side reactions lower the actual yield and complicate purification.
- Overall yield – The cumulative percent yield for a multi-step synthesis, calculated by multiplying the individual percent yields of each step. For a three-step synthesis with 80% yield per step, the overall yield is 0.80 × 0.80 × 0.80 = 51.2%.
- Purification – The process of isolating the desired product from reaction mixtures by removing impurities, byproducts, and unreacted starting materials. Common purification methods include recrystallisation, column chromatography, distillation, and sublimation.
How to Use?
- 1
Select calculation mode
Choose "Percent yield (actual vs theoretical)" for single reactions or "Overall yield (multi-step)" for synthetic sequences. The inputs adjust automatically.
- 2
Enter actual yield
Type the mass of product you obtained. Use the unit dropdown to switch between grams, milligrams, or kilograms.
- 3
Enter theoretical yield
Input the calculated maximum mass from stoichiometry. The same unit choices are available.
- 4
Review the result
The calculator shows the percent yield, the mass lost, and a colour-coded status indicator: green for excellent, yellow for good, red for poor.
- 5
Use multi-step mode (optional)
Switch to "Overall yield" mode and enter the percent yield of each synthetic step (2 or 3 steps). The overall yield is calculated as the product of individual step yields.
Frequently Asked Questions
Percent yield is the ratio of the actual amount of product obtained from a reaction to the theoretical maximum amount predicted by stoichiometry, multiplied by 100%. It is the standard metric for measuring reaction efficiency. A yield of 90% or higher is considered excellent for most synthetic reactions.
Percent yield is usually below 100% because of incomplete reactions where equilibrium limits conversion, side reactions that consume starting material to form byproducts, physical losses during transfer and purification, and measurement uncertainties. Even a well-executed reaction rarely exceeds 95% isolated yield when purification losses are accounted for.
A yield above 100% almost always indicates that the product is impure. Residual solvent, unreacted starting material, or byproducts add mass that is not the desired compound. Incomplete drying is the most frequent cause. A small amount of water or ethyl acetate trapped in the product can easily add 5–10% to the mass. Check purity by NMR or HPLC before reporting the yield.
Optimise reaction time and temperature to ensure complete conversion. Use a slight excess of one reagent to drive the equilibrium. Add a catalyst to lower the activation energy. Minimise side reactions by controlling temperature and using selective reagents. Reduce purification losses by rinsing glassware, combining washings, and using minimal chromatography solvent. Each improvement compounds across the procedure.
Percent yield measures how much product you isolated versus the theoretical maximum. Atom economy measures what fraction of the starting material atoms end up in the product versus waste. A reaction can have 100% yield but poor atom economy (e.g., Wittig reaction), or excellent atom economy but low yield (e.g., equilibrium-limited Diels-Alder). Both are important for green chemistry.
Follow four steps: (1) write and balance the chemical equation, (2) identify the limiting reagent using mole ratios, (3) convert the mass of the limiting reagent to moles using its molar mass, (4) use the stoichiometric coefficients to find moles of product and convert to mass using the product's molar mass. For aspirin from 2.00 g salicylic acid: 2.00 / 138.12 = 0.01448 mol × 180.16 g/mol = 2.61 g theoretical yield.
If you use the excess reagent instead of the limiting reagent, the theoretical yield will be too high and the percent yield will appear artificially low. If you use a reactant that is not actually limiting, the theoretical yield will be wrong in the opposite direction. Always calculate moles of each reactant, divide by the stoichiometric coefficient, and identify the smallest value as the limiting reagent.
Multiply the decimal yields of each step together and convert back to a percentage. For a three-step sequence with step yields of 85%, 78%, and 92%: 0.85 × 0.78 × 0.92 = 0.610, or 61.0% overall. The multi-step mode of this calculator performs this calculation automatically. You can enter two or three step yields and get the overall result instantly.
Conversion is the fraction of starting material that has reacted, regardless of what it formed. Selectivity is the fraction of reacted starting material that went to the desired product. Yield (actually isolated yield) is conversion × selectivity × recovery efficiency. A reaction can have 100% conversion but 0% yield if all the starting material forms byproducts that are discarded during purification.
If the isolated product contains impurities, the measured mass overstates the true yield. A sample that appears to give 95% yield may be only 85% pure by HPLC, meaning the actual yield of pure product is 81%. Always report both the isolated yield and the purity. For regulatory submissions, the purity-corrected yield is the more meaningful number.
Palladium-catalysed cross-couplings (Suzuki, Sonogashira) typically give 70–95%. Diels-Alder reactions often reach 80–98%. Fischer esterifications are equilibrium-limited and usually give 60–85%. Grignard reactions range from 75–95%. Amide couplings with modern coupling reagents routinely give 75–95%. The reference table in this calculator lists typical ranges for twelve common reaction types.
Percent yield is one of several metrics used alongside atom economy, E-factor (kg waste per kg product), and process mass intensity (PMI). The ACS Green Chemistry Institute recommends tracking all four. A reaction with 90% yield and low PMI is greener than one with the same yield but high solvent usage. Percent yield alone does not capture environmental impact, but it is a necessary component of any green chemistry assessment.
Chemical yield refers specifically to the amount of product formed from a chemical transformation, measured against the theoretical maximum. Recovery refers to the amount of material retrieved after a non-reactive operation such as recrystallisation, distillation, or chromatography. Recovery can approach 100% with careful technique, while chemical yield is fundamentally limited by reaction thermodynamics and side reactions.
Report the isolated yield of pure product after purification, not the crude yield. Specify the purity assessment method (NMR, HPLC, melting point). For multi-step sequences, report the yield of each individual step and the overall yield. Include the scale in grams or millimoles. A typical journal format: "Compound 7 (85 mg, 72% yield) was obtained as a white solid after column chromatography." Reproducibility requires complete experimental details.
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