Theoretical Yield Calculator
Find the theoretical yield of any product from any set of reactant amounts, with the limiting reactant identified automatically, an optional percent yield check, and full step-by-step working.
Type your equation, enter how much of each reactant you have, and pick which product to calculate.
Theoretical yield of CO2
131.7366 g
Equivalent to 2.9934 mol, limited by C3H8
0.9978
Reaction extent (mol)
44.009 g/mol
Molar mass of CO2
C3H8
Limiting reactant
83.5%
Percent yield
Yield & Reactant Comparison
See the theoretical yield of every product, and which reactant limits the reaction.
Step-by-Step Theoretical Yield Calculation
Here's exactly how this answer was calculated, one step at a time.
Given: C3H8 + O2 -> CO2 + H2O
Step 1: Balance the chemical equation
The coefficients in the balanced equation set the exact mole ratio between every reactant and every product.
C3H8 + 5 O2 -> 3 CO2 + 4 H2OStep 2: Convert every reactant amount into moles
C3H8: 44 g = 0.9978 mol (M = 44.097 g/mol) | O2: 160 g = 5.00031 mol (M = 31.998 g/mol)Step 3: Divide each reactant's moles by its coefficient
The smallest result marks the limiting reactant — the one that runs out first and caps how much product can form.
C3H8: 0.9978 ÷ 1 = 0.9978 | O2: 5.00031 ÷ 5 = 1.00006Step 4: Identify the limiting reactant
C3H8 gives the smallest ratio (0.9978), so C3H8 is the limiting reactant.Step 5: Use the mole ratio to find moles of CO2
This mole ratio comes straight from the balanced equation's coefficients — 3 mol of CO2 forms for every complete "set" of the reaction.
moles of CO2 = 0.9978 × 3 = 2.9934 molStep 6: Convert moles of CO2 to mass
This is the theoretical yield: the maximum mass of product the reaction can form, assuming everything reacts perfectly.
mass = 2.9934 mol × 44.009 g/mol = 131.7366 gStep 7: Calculate percent yield (optional)
Percent yield compares the actual mass you recovered in the lab to the theoretical maximum this calculator predicts.
percent yield = (110 g ÷ 131.7366 g) × 100 = 83.5%
Theoretical yield of CO2:
131.7366 g
Theoretical Yield Calculator: Find the Maximum Product Yield Online
This theoretical yield calculator works out the maximum mass of product a chemical reaction can form, based on the exact amounts of reactants you start with. Type your equation, enter how much of each reactant you have, pick the product you care about, and it returns the theoretical yield in grams and moles, along with the limiting reactant that controls the whole calculation.
It's built for chemistry students working through stoichiometry problems, lab teams planning a synthesis, and anyone who needs a fast, dependable way to predict how much product a reaction should give. Every result comes with the full step-by-step method underneath, and there's a built-in percent yield check too, so you can compare your real lab result against the theoretical maximum in the same place.
What Does Theoretical Yield Actually Mean?
Theoretical yield is the maximum amount of product a reaction can produce, assuming the reaction goes to completion with no losses, no side reactions, and no reactant left unreacted beyond what's unavoidable. It's a ceiling, not a promise — real reactions almost always produce a bit less than this number.
This ceiling is set entirely by the limiting reactant, the reactant that runs out first. Once it's used up, the reaction stops, no matter how much of the other reactants remain. Theoretical yield tells you exactly how much product that limiting reactant is capable of forming, based on the mole ratio written into the balanced equation.
How to Calculate Theoretical Yield Step by Step
Start by writing a balanced chemical equation, since the coefficients define the exact ratio reactants combine in and products form in. Next, convert every reactant's given amount into moles using its molar mass, because grams from different substances aren't directly comparable.
Then, for every reactant, divide its moles by its coefficient in the balanced equation. The smallest of these values identifies the limiting reactant and sets what's called the reaction extent. Multiply that extent by the coefficient of the product you're interested in to get its moles formed, then multiply by its molar mass to convert that into a mass — that final mass is the theoretical yield. This calculator runs through every one of these steps automatically and shows the full working.
The Theoretical Yield Formula
In formula terms: theoretical yield (grams) = moles of limiting reactant × (coefficient of product ÷ coefficient of limiting reactant) × molar mass of product. The middle part of that formula is the mole ratio taken straight from the balanced equation, and it's the piece most students get wrong when they skip balancing the equation first.
This calculator never skips that step — it balances your equation automatically before running any yield calculation, so the mole ratio used is always correct, even for equations with several reactants and several products, like combustion reactions or acid-base neutralisations.
Theoretical Yield vs Actual Yield vs Percent Yield
Theoretical yield is the maximum possible amount of product, calculated purely from stoichiometry. Actual yield is what you actually measure in the lab once the reaction is done, weighed and purified — it's almost always a little lower, because of side reactions, incomplete reactions, or product lost during purification.
Percent yield ties the two together: percent yield = (actual yield ÷ theoretical yield) × 100. This calculator includes an optional actual yield field for exactly this reason — enter what you actually recovered, and it calculates your percent yield instantly, right next to the theoretical figure it just worked out.
Why the Limiting Reactant Decides Theoretical Yield
It's tempting to calculate theoretical yield from whichever reactant you have the most of, but that's usually wrong. Only the limiting reactant — the one that runs out first — determines the maximum product possible. Every other reactant simply has leftover excess once the reaction stops.
This is why this calculator asks for the amount of every reactant, not just one. It works out the limiting reactant internally before calculating yield, which avoids the single most common error in theoretical yield problems: assuming the wrong reactant controls the reaction.
Worked Example: Theoretical Yield of Carbon Dioxide from Propane
Take the combustion reaction C3H8 + 5O2 -> 3CO2 + 4H2O. Suppose you start with 44 grams of propane and 160 grams of oxygen gas. Propane's molar mass is about 44.1 g/mol, giving roughly 1.00 mol of C3H8. Oxygen's molar mass is about 32.0 g/mol, giving roughly 5.00 mol of O2.
Dividing by coefficients: propane gives 1.00 ÷ 1 = 1.00, and oxygen gives 5.00 ÷ 5 = 1.00 — in this case, both reactants run out at exactly the same point, so either one can be treated as limiting. Using a reaction extent of 1.00 mol, the moles of CO2 formed are 1.00 × 3 = 3.00 mol, which at a molar mass of about 44.0 g/mol gives a theoretical yield of roughly 132 grams of carbon dioxide — the exact figure this calculator returns instantly.
Common Mistakes When Calculating Theoretical Yield
The most frequent mistake is using the wrong reactant's moles directly, without first checking which one is limiting. If you assume the reactant you have the most grams of is automatically the one in excess, you can end up basing the whole yield calculation on the wrong number.
Another common mistake is forgetting to apply the mole ratio between the limiting reactant and the product — simply carrying the limiting reactant's mole count straight over to the product, instead of scaling it by the ratio of their coefficients. A third mistake is converting moles back to mass using the wrong substance's molar mass. This calculator applies each of these steps in the correct order automatically, every time.
Why Theoretical Yield Matters Beyond the Classroom
Theoretical yield calculations sit at the center of planning any real chemical process. A process chemist scaling a reaction from a small lab flask to a full production batch needs to know the maximum product a given amount of raw material can deliver, so the batch size and material orders can be planned accurately.
In pharmaceutical manufacturing, theoretical yield calculations help estimate how much active ingredient a synthesis step can realistically produce, which feeds directly into cost and scheduling decisions. Environmental and materials chemists use the same math to predict how much of a target compound a given reaction setup can generate before ever running it.
Understanding Why Actual Yield Is Almost Always Lower
Real reactions rarely hit their theoretical yield exactly. Side reactions can consume some of the limiting reactant in ways the main equation doesn't account for, reducing how much of the intended product actually forms. Reversible reactions may not go fully to completion, leaving some reactant unconverted even without side reactions.
Physical losses matter too — product can stick to glassware, get lost during filtration, or be left behind in a solvent during purification. None of these reduce the theoretical yield itself, since that's a purely mathematical ceiling, but they're exactly why percent yield is almost always below 100%, and why comparing actual to theoretical yield is such a useful check on how a real procedure performed.
How to Enter Your Reaction Correctly
Type your equation using standard chemical notation — a capital letter to start each element symbol, a lowercase letter if the symbol has two letters, and a number directly after an element for its subscript, like Ca(OH)2 or C6H12O6. Separate compounds on the same side with a plus sign, and separate reactants from products with an arrow (->) or an equals sign.
You don't need to balance the equation yourself — this calculator does that automatically. Once it's entered, a box appears for every reactant so you can type in how much you're starting with, in whichever unit suits your data, and a dropdown lets you pick which product you want the theoretical yield of, useful for reactions that form more than one product at once.
Using Percent Yield to Check Your Lab Result
Once you've actually run a reaction and weighed your purified product, enter that mass in the optional actual yield field. This calculator immediately compares it to the theoretical yield it just calculated and reports your percent yield, without any extra steps or a second calculator.
A percent yield close to 100% usually means a clean, efficient reaction and good technique during purification. A low percent yield is worth investigating — it can point to side reactions, an incomplete reaction, or product lost somewhere during workup, and knowing the theoretical yield precisely is the first step toward figuring out where that loss happened.
Theoretical Yield Calculator FAQ and Quick Reference
To calculate theoretical yield, balance the equation, convert every reactant to moles, find the limiting reactant by dividing moles by coefficients, then use the mole ratio between the limiting reactant and the product to calculate the product's mass. That mass is the theoretical yield.
This free online theoretical yield calculator is built for homework help, exam revision, and quick lab planning. For regulated, safety-critical, or large-scale industrial use, always double-check every formula, molar mass, and quantity against a certified reference before relying on it for a real procedure.
Frequently Asked Questions
How do you calculate theoretical yield?
Balance the equation, convert every reactant to moles, find the limiting reactant, then use the mole ratio between the limiting reactant and the product to calculate the product's mass — that mass is the theoretical yield.
What is the theoretical yield formula?
Theoretical yield = moles of limiting reactant × (coefficient of product ÷ coefficient of limiting reactant) × molar mass of product.
What's the difference between theoretical yield and actual yield?
Theoretical yield is the maximum possible amount of product predicted by stoichiometry. Actual yield is the amount you actually measure after running and purifying the reaction, and it's almost always a little lower.
How is percent yield calculated from theoretical yield?
Percent yield = (actual yield ÷ theoretical yield) × 100. This calculator works it out automatically once you enter an actual yield.
Why is theoretical yield always based on the limiting reactant?
The limiting reactant runs out first and stops the reaction, so it's the only reactant that actually determines the maximum amount of product that can form.
Can this calculator handle reactions with more than one product?
Yes. Once the equation is balanced, a dropdown lets you choose exactly which product you want the theoretical yield of, and the chart shows the yield of every product side by side.