Last updated: July 3, 2026
Theoretical Yield Calculator
Creators
Dharmendra SinghReviewers
Creators
Dharmendra SinghReviewers
Quick Answer
This calculator finds theoretical yield in grams from limiting-reactant stoichiometry or by rearranging actual yield and percent yield. It reports the maximum product mass, limiting reactant moles, product moles, mole ratio, and an interpretation.
The theoretical yield is the maximum product mass predicted from the limiting reactant. Convert limiting reactant grams to moles, apply the product-to-reactant mole ratio, then multiply by product molar mass.
Key Takeaways
- Theoretical yield is the stoichiometric maximum product amount.
- The limiting reactant, not the excess reactant, sets the product ceiling.
- Mass-based calculations must pass through moles before applying coefficients.
- Product molar mass converts stoichiometric product moles into grams.
- Actual yield divided by percent yield as a decimal recovers theoretical yield.
Creators
Dharmendra SinghReviewers
Creators
Dharmendra SinghReviewers
Formula
theoretical yield = n(limiting reactant) × (coefficient product / coefficient reactant) × molar mass product; or actual yield ÷ (percent yield/100)
Where:
- Ytheoretical=Maximum product mass predicted by stoichiometry(g)
- nlimiting=Moles of limiting reactant(mol)
- νproduct/νreactant=Balanced-equation mole ratio from reactant to product(mol product/mol reactant)
- Mproduct=Molar mass of desired product(g/mol)
- %Y=Percent yield for rearranged actual-yield checks(%)
Worked Examples
Maximum product from 10 g of limiting reactant
A 10 g limiting reactant has molar mass 40 g/mol, reacts 1:1, and forms a product with molar mass 100 g/mol.
- 1Convert limiting reactant to moles: 10 g ÷ 40 g/mol = 0.25 mol.
- 2Apply the 1:1 mole ratio, so product moles = 0.25 mol.
- 3Multiply by product molar mass: 0.25 mol × 100 g/mol = 25 g.
- 4This is the maximum product mass before losses or side reactions.
Feedstock analog giving 44 g product
A 36 g limiting reactant with molar mass 36 g/mol reacts 1:1 to a 44 g/mol product.
- 1Convert mass to amount: 36 g ÷ 36 g/mol = 1.00 mol.
- 2The balanced equation ratio is 1 mol product per 1 mol reactant.
- 3Product amount is 1.00 mol.
- 4Theoretical yield = 1.00 mol × 44 g/mol = 44 g.
Recover theoretical yield from 90% yield
An experiment isolated 45 g of product and the percent yield was 90%.
- 1Use theoretical yield = actual yield ÷ (percent yield / 100).
- 2Convert percent yield to a decimal: 90 / 100 = 0.90.
- 3Divide: 45 g ÷ 0.90 = 50 g.
- 4The stoichiometric ceiling was 50 g.
Find the ceiling behind an 80% run
A reaction produced 20 g actual product at 80% yield.
- 1Use theoretical yield = actual yield ÷ (percent yield / 100).
- 2Convert 80% to 0.80.
- 3Compute 20 g ÷ 0.80 = 25 g.
- 4A perfect stoichiometric run would correspond to 25 g.
Use a 2:1 product-to-reactant mole ratio
Five moles of limiting reactant produce product in a 2:1 ratio, and the product molar mass is 18 g/mol.
- 1Start directly with 5 mol of limiting reactant.
- 2Apply the ratio: 5 mol × (2/1) = 10 mol product.
- 3Convert product moles to grams: 10 mol × 18 g/mol = 180 g.
- 4The theoretical yield is the maximum predicted mass.
Introduction
Theoretical yield is the maximum amount of product a balanced chemical equation permits from the limiting reactant. It is a stoichiometric ceiling, not a promise that the lab will recover that much product. This calculator supports two practical workflows: start from limiting-reactant mass or moles and convert through the mole ratio to product grams, or rearrange actual yield and percent yield to recover the theoretical yield used in a lab report.
Theoretical yield formula
For a limiting reactant calculation, use theoretical yield = moles limiting reactant × (product coefficient/reactant coefficient) × product molar mass. If the limiting reactant is given in grams, first compute moles = mass ÷ molar mass. Formula masses are often the first bottleneck, so the molar mass calculator is a useful companion before this yield step.
Identify the limiting reactant, not just any reactant.
Convert grams to moles before using a balanced-equation coefficient ratio.
Use the product molar mass to convert product moles back to grams.
Report theoretical yield as the maximum possible product, usually in grams.
How to calculate theoretical yield step by step
Balance the equation, convert each relevant reactant amount to moles, divide by its stoichiometric coefficient to find the limiting reactant, then convert that limiting amount into target product. In the simple 10 g example, 10 g ÷ 40 g/mol = 0.25 mol; a 1:1 ratio gives 0.25 mol product; multiplying by 100 g/mol gives 25 g. Once a reaction is run, compare actual recovery with the percent yield calculator.
Keep mole ratios as exact coefficient ratios and round only the final gram value.
Why the limiting reactant sets the ceiling
The limiting reactant runs out first, so it caps the amount of product that can form even if other reagents remain in excess. This is why theoretical yield is tied to the limiting reactant rather than the largest mass in the flask. Standard stoichiometry treatments, including OpenStax Chemistry 2e, emphasize converting to moles before comparing reactants.
Recover theoretical yield from percent yield
If actual product mass and percent yield are known, rearrange the yield relation: theoretical yield = actual yield ÷ (percent yield/100). For example, 45 g actual at 90% yield corresponds to 45 ÷ 0.90 = 50 g theoretical. This mode is useful when auditing lab data or checking whether an entered theoretical yield agrees with an observed product mass. The companion actual yield calculator solves the forward recovery question.
Percent yield must be greater than zero because it appears in the denominator.
Units, mole ratios, and product mass
Stoichiometry works in moles, while product reporting often uses grams. A coefficient ratio such as 2:1 means two moles of product per one mole of limiting reactant; it is not a mass ratio. After the mole-ratio step, product molar mass converts moles to grams. For atomic-weight traceability, resources such as NIST Chemistry WebBook and IUPAC Gold Book help define quantities and data sources.
| Quantity | Role |
|---|---|
| Limiting reactant moles | Starting amount that caps product |
| Product/reactant ratio | Balanced equation conversion factor |
| Product molar mass | Converts product moles to grams |
| Theoretical yield | Maximum product mass |
Common theoretical-yield mistakes
Common errors include using excess reactant data, applying a mass ratio instead of a mole ratio, forgetting to divide by reactant molar mass, or calculating actual yield when the question asks for the theoretical maximum. If your theoretical yield is lower than the actual mass you claim to have isolated, recheck purity, drying, units, and the balanced equation. For reaction amount work beyond yield, the molarity calculator can connect moles with solution volume.
Quick Reference Card
Theoretical yield quick guide
Quick reference • Theoretical Yield Calculator
Ytheoretical = nlimiting × (νproduct/νreactant) × MproductValid range: All masses, molar masses, coefficients, and percent yields must be non-negative; denominators must be greater than zero.
Common Values
⚠ Watch Out
- •Do not use the excess reactant to set theoretical yield.
- •Do not apply balanced coefficients to grams directly.
- •Percent yield must be greater than zero in from-percent mode.
- •Check that product molar mass corresponds to the desired product formula.
Pro Tips
- →Balance the chemical equation before entering mole ratios.
- →Use direct moles if the limiting reactant amount is already known.
- →Carry extra digits through molar-mass and mole-ratio steps.
- →Compare actual yield to theoretical yield only after units match.
FAQs
What is theoretical yield?
Theoretical yield is the maximum product amount predicted by balanced-equation stoichiometry from the limiting reactant. It assumes complete reaction and no losses.
How do I find theoretical yield from grams of reactant?
Convert the limiting reactant mass to moles, multiply by the balanced-equation product-to-reactant mole ratio, then multiply by the product molar mass to obtain grams of product.
Can theoretical yield be calculated from percent yield?
Yes. If actual yield and percent yield are known, theoretical yield equals actual yield divided by percent yield as a decimal.
Is theoretical yield the same as actual yield?
No. Theoretical yield is the ideal maximum. Actual yield is what is isolated or measured after the reaction, workup, purification, and drying.
Why must I use the limiting reactant?
Only the limiting reactant determines how many reaction cycles can occur. Excess reactants remain after the limiting reactant is consumed, so they cannot raise the maximum product beyond that ceiling.
What if the product-to-reactant ratio is not 1:1?
Use the balanced coefficients directly. For a 2:1 product-to-reactant ratio, each mole of limiting reactant can form two moles of product before converting to grams.