Percent Yield Calculator - Actual, Theoretical, Molar Mass

Q: What formulas can the Molar Mass Helper read?

It reads normal formulas like H2O and NaCl , groups in parentheses or brackets like Ca(OH)2 and Al2(SO4)3 , and hydrates written with * or · like CuSO4*5H2O . Capital letters matter: Co is cobalt, CO is carbon and oxygen.

Q: Is percent yield the same as purity?

No. Percent yield says how much product you got. Purity says how clean that product is. You can have a 95% yield of a dirty, wet solid. A high yield with low purity often means your sample still holds solvent or leftover reactant.

% Yield Calculator

Updated Aug 28, 2026 By Jehan Wadia

Introduction

When you run a chemical reaction, you almost never get as much product as the math says you should. Some product sticks to the glass, some spills, and some reactions just don't finish. The percent yield tells you how much you really got compared to how much you could have gotten.

This % yield calculator does that math for you. Enter your actual yield (what you weighed in the lab) and your theoretical yield (what stoichiometry predicts), and it gives you the percent yield right away. You can also flip it around: give it the percent yield plus one of the two amounts, and it will find the missing one.

The formula is simple:

% Yield = (Actual Yield ÷ Theoretical Yield) × 100

You can work in grams, milligrams, kilograms, micrograms, pounds, ounces, or moles. The tool converts units for you and warns you if two units don't match. A built-in molar mass helper lets you type a formula like C6H12O6 or CuSO4*5H2O and get the molar mass in g/mol — the same job handled by our Molecular Weight Calculator.

Every answer comes with step-by-step work, a summary, a yield rating, and charts so you can see how your actual yield stacks up against the theoretical one. It's built for chemistry students, lab classes, and anyone checking how well a reaction worked. If you still need to find that theoretical number from a balanced equation, start with the Stoichiometry Calculator.

How to Use Our Percent Yield Calculator

Enter two of the three yield values — actual yield, theoretical yield, or percent yield — and the calculator finds the missing one. It also shows your step-by-step math, an efficiency rating, and charts that compare your actual and theoretical yield.

Choose What to Solve For: Pick "Find % Yield," "Find Actual Yield," or "Find Theoretical Yield." The box you pick turns into the answer box, and you fill in the other two.

Actual Yield: Type the amount of product you really got from your reaction, then pick a unit like g, mg, kg, µg, lb, oz, or mol. To switch between grams and moles, use the Mole Calculator.

Theoretical Yield: Type the largest amount of product the reaction could make on paper, then pick its unit. Both yield units must match in type — mass with mass, or moles with moles. For quick unit swaps like grams to ounces, try the Grams to Ounces Calculator or the general Unit Converter Calculator.

Percent Yield: Type the percent yield if you already know it. This value has no unit and must be between 0 and 100. For plain part-of-whole math outside the lab, the Percentage Calculator works well.

Rounding / Precision: Choose how many decimal places you want in the answer, or leave it on Auto for 4 significant figures. Lab reports often demand a set number of digits — the Sig Fig Calculator and the Rounding Calculator can help you match your instructor's rules.

Chemical Formula (Molar Mass Helper): Type a formula like H2O, Ca(OH)2, or CuSO4*5H2O and click "Compute Molar Mass" to see the molar mass and a breakdown of each element. Then click "Use as Actual Yield (g)" or "Use as Theoretical Yield (g)" to drop that number straight into the calculator.

Calculate and Reset: Click Calculate to see your result, summary, and steps. Click Reset to clear everything and start over.

What Is Percent Yield?

Percent yield tells you how much product a chemical reaction really made compared to how much it should have made. It is written as a percent. A high percent yield means the reaction worked well. A low percent yield means you lost product along the way.

The Percent Yield Formula

% Yield = (Actual Yield ÷ Theoretical Yield) × 100

You can also flip the formula around to find a missing value:

Actual Yield = (% Yield ÷ 100) × Theoretical Yield
Theoretical Yield = Actual Yield ÷ (% Yield ÷ 100)

At heart this is just a ratio scaled to 100, so the Ratio Calculator can double-check the fraction step if you want.

Actual Yield vs. Theoretical Yield

Actual yield is the amount of product you really collected and weighed in the lab. You measure it on a balance.

Theoretical yield is the largest amount of product the reaction could make. You find it with stoichiometry: start with the limiting reactant, change grams to moles using molar mass, use the mole ratio from the balanced equation, then change moles back to grams. The Stoichiometry Calculator walks through that chain, and the Molecular Weight Calculator supplies the molar masses you need.

Why Yields Are Less Than 100%

Almost every reaction gives less than the full amount. Common reasons:

Some product sticks to the flask, filter paper, or stir rod.
Side reactions make other products you did not want.
The reaction does not finish or reaches equilibrium.
Product is lost during filtering, drying, or moving between containers.
Starting materials were not pure — sloppy solution prep is a frequent culprit, so check your work with the Molarity Calculator or the Dilution Calculator.

What Counts as a Good Yield?

90% and up: excellent
75–89%: good
50–74%: moderate
Under 50%: poor

Over 100% Yield

A percent yield above 100% is not possible in real chemistry. If you get one, your product is probably still wet with solvent, or it holds leftover reactant or other impurities. Dry the sample fully and weigh it again. To measure how far your number strays from an accepted value, use the Percent Error Calculator or compare two readings with the Percent Difference Calculator.

Units Matter

Both yields must use the same kind of unit. You can compare grams to grams, or moles to moles, but you cannot compare grams to moles unless you use the molar mass to convert first. Gas-phase products may need the Ideal Gas Law Calculator to turn volume into moles, and liquids may need the Density Calculator to turn volume into mass. Because percent yield is a ratio, the units cancel out, so the answer has no unit — just a percent sign.

Where Percent Yield Is Used

Students use it in chemistry class labs to check their work, then roll the result into a lab report score with the Grade Calculator. Chemists in drug and material companies use it to see if a process is worth the cost. A low yield can mean wasted money and wasted starting material, so labs work hard to raise it — and improvements are often tracked as a percentage increase from batch to batch. Related bench tools include the pH Calculator, the PPM Calculator, and the Serial Dilution Calculator.

Formulas used

Percent Yield

\%\text{ Yield} = \frac{\text{Actual Yield}}{\text{Theoretical Yield}} \times 100

Actual Yield

\text{Actual Yield} = \frac{\%\text{ Yield}}{100} \times \text{Theoretical Yield}

Theoretical Yield

\text{Theoretical Yield} = \frac{\text{Actual Yield}}{\%\text{ Yield} / 100}

Unit conversion to a common base unit

V_{\text{base}} = V_{\text{unit}} \times f_{\text{unit}}, \qquad V_{\text{unit}} = \frac{V_{\text{base}}}{f_{\text{unit}}}

Product not recovered (unrecovered amount)

\text{Lost} = \text{Theoretical Yield} - \text{Actual Yield}

Percent not recovered

\%\text{ Unrecovered} = 100 - \%\text{ Yield}

Molar mass from chemical formula

M = \sum_{i} n_i \cdot A_i

Frequently asked questions

Do I need a balanced equation to use this calculator?

Not for this tool. This calculator only compares two numbers: actual yield and theoretical yield. But you do need a balanced equation to find the theoretical yield in the first place. Work that part out first, then bring the number here.

Why is one of my input boxes locked?

The box you picked in "Choose What to Solve For" becomes the answer box. It is shaded and marked Result, so you cannot type in it. Fill in the other two boxes and click Calculate. To unlock it, pick a different mode.

Why do I get an error saying my units are incompatible?

You mixed a mass unit with moles. Grams, mg, kg, µg, lb, and oz are all mass. Moles are a count of particles. The tool cannot compare them without a molar mass. Set both boxes to mass units, or set both to mol.

Can I enter one yield in grams and the other in milligrams?

Yes. Any two mass units work together. The calculator converts both to grams behind the scenes and shows the conversion as its own step. For example, 4,500 mg and 6 g give the same 75% as 4.5 g and 6 g.

How do I change moles into grams so my units match?

Multiply the moles by the molar mass in g/mol.

Use the Molar Mass Helper to get the g/mol for your product.
Multiply: moles × g/mol = grams.
Type that gram value into the yield box.

What formulas can the Molar Mass Helper read?

It reads normal formulas like H2O and NaCl, groups in parentheses or brackets like Ca(OH)2 and Al2(SO4)3, and hydrates written with * or · like CuSO4*5H2O. Capital letters matter: Co is cobalt, CO is carbon and oxygen.

What do the two "Use as" buttons do?

They copy the molar mass number straight into a yield box in grams. This is handy when you already worked in moles and want the mass of one mole. Check that the number makes sense for your lab before you calculate.

What does "Auto (4 significant figures)" mean?

Auto keeps the first four meaningful digits of your answer, like 75.00% or 0.7856 g. If your teacher wants a set number of decimals instead, pick 0 through 8 from the same menu.

Is percent yield the same as purity?

No. Percent yield says how much product you got. Purity says how clean that product is. You can have a 95% yield of a dirty, wet solid. A high yield with low purity often means your sample still holds solvent or leftover reactant.

Is percent yield the same as percent error?

No. Percent yield compares what you made to the most you could make. Percent error compares your measured value to a known correct value. They use different formulas and answer different questions.

Does the percent yield change if I measure a different product?

Yes. A reaction can make more than one product. Each product has its own theoretical yield and its own percent yield. Always say which product your number is for.

Why does my percent yield stay low even when I follow the steps?

Common causes are wet or impure starting material, losing solid on filter paper, boiling off product while heating, and reactions that stop early. Try weighing your losses at each step to find where the product goes.

What is the "yield ratio" in the summary?

It is the actual yield divided by the theoretical yield, before you multiply by 100. A ratio of 0.75 is the same as 75%. Some teachers ask for this decimal form instead of a percent.

What do the gauge and bar charts show?

The gauge shows your percent yield on a 0–100 scale, colored by how good it is. The bar chart puts your actual yield next to your theoretical yield in the same unit, so you can see the gap at a glance.

Why can I type a percent over 100 in one mode but not the others?

In "Find % Yield" mode the percent is the answer, so the tool will report a value above 100 and warn you about it. In the other two modes you type the percent yourself, and it must be 0–100 so the result stays realistic.

Can actual yield be zero?

Yes. If you got no product, the actual yield is 0 and the percent yield is 0%. The theoretical yield can never be zero, though, because you cannot divide by zero.

Can I use this calculator outside of chemistry?

Yes. Any "got versus expected" job works: crop harvests, factory output, or recipe batches. Just keep both amounts in the same unit type.

Does the calculator save my numbers?

No. Nothing is stored. Reset clears everything back to the starting example, and closing the page wipes your entries. Write down or screenshot results you want to keep.