Chemical Batch Yield and Mass Balance Calculator
Yield is the first number a plant manager checks after a batch. This calculator converts the limiting reagent charge to a theoretical product mass, corrects the isolated product for purity and shows how much of the gap is explained by known losses.
Your numbers
Pure basis. Correct for assay if the charge is not 100%.
From the balanced equation.
Your results
For a single reaction with one limiting reagent. Real batches may have side reactions, recycled streams and moisture. Use your validated mass balance for reporting. Example defaults use salicylic acid to aspirin on a 1:1 basis, illustrative only.
Percent yield vs product purity
Sweeps Product purity (assay) from 80 to 100, holding your other inputs fixed.
Yield trend report from ERP data
Optional: discuss reporting batch yield and variance from your ERP production orders.
Optional. The tool and every export work without this. No spam.
How to use the calculator
Enter the mass of limiting reagent charged, its molecular weight, the product's molecular weight and the stoichiometric ratio from the balanced equation. Then enter the gross mass of product isolated and its assay. Known losses are samples, vessel heels, filter cake retained and other measured amounts. The result shows percent yield, the gap in kilograms and what remains unexplained.
The formulas
Theoretical yield equals reagent moles times the stoichiometric ratio times product molecular weight. Percent yield equals actual pure product divided by theoretical yield, times 100. Mass balance compares total input with total output, including waste and samples. A large unaccounted number usually points to measurement error, unrecorded transfers, evaporation or a side reaction.
- kmol = kg / (g/mol)
- Theoretical kg = kmol x ratio x product MW
- Pure product = gross x assay / 100
- Yield % = pure product / theoretical x 100
Worked example
With 500 kg of a reagent at MW 138.12, there are 3.62 kmol. At a 1:1 ratio and a product MW of 180.16, theoretical yield is about 652 kg. If 560 kg of 99% product is isolated, pure product is 554 kg, so yield is about 85%. The 98 kg gap less 12 kg of known losses leaves about 86 kg unaccounted, which merits investigation of side reactions or mother liquor losses.
Common mistakes
Common mistakes are using the wrong limiting reagent, ignoring assay of the starting material, mixing wet and dry weights, using the wrong molecular weight for hydrates and forgetting recycle streams. Always state the basis, and compare trend over many batches rather than reacting to one number.
Frequently Asked Questions
What is a good percent yield?
It depends on the chemistry. Simple blends should be close to 100%, while multi-step syntheses can be far lower. Compare to your own historical average for the same process rather than a generic target.
Why can yield exceed 100%?
Usually from residual solvent or moisture in the product, impurities, a wrong molecular weight or a weighing error. Check purity and drying before accepting the number.
How do I handle a reagent that is not pure?
Multiply the charged mass by its assay percentage divided by 100 before entering it, so the calculation uses the pure reagent only.
Is yield the same as mass balance closure?
No. Yield compares product to theory. Mass balance closure compares all outputs, including waste and losses, with all inputs. Both are useful and answer different questions.
Netray can help pull batch charge and output quantities from ERP production orders to track yield trends and cost impact automatically.
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