Last updated: July 3, 2026
Percent Yield Calculator
Creators
Dharmendra SinghReviewers
Creators
Dharmendra SinghReviewers
Quick Answer
Percent yield compares actual product recovered with the theoretical maximum from stoichiometry. Calculate it by dividing actual yield by theoretical yield and multiplying by 100. For example, 45 g actual from 50 g theoretical gives 90%, which is an excellent yield by common teaching-lab bands.
Percent yield equals actual yield divided by theoretical yield times one hundred. For example, forty-five grams actual from fifty grams theoretical is ninety percent yield.
Key Takeaways
- Percent yield = (actual yield / theoretical yield) × 100.
- Use actual and theoretical yield in the same unit, such as grams with grams or moles with moles.
- A 45 g actual yield from a 50 g theoretical yield equals 90%, an excellent yield band.
- Percent yield above 100% usually signals wet product, impurity, weighing error, or incorrect stoichiometry.
- The equation can also solve for actual yield or theoretical yield when percent yield is known.
Creators
Dharmendra SinghReviewers
Creators
Dharmendra SinghReviewers
Formula
percent yield = (actual yield / theoretical yield) × 100
Where:
- %Y=Percent yield of the reaction(%)
- Yactual=Actual yield measured after isolation(g or mol)
- Ytheoretical=Theoretical yield predicted by stoichiometry(g or mol)
Worked Examples
Calculate a 90% percent yield
A reaction produces 45 g of product when the theoretical yield is 50 g.
- 1Use percent yield = (actual yield / theoretical yield) × 100.
- 2Substitute the values: percent yield = (45 g / 50 g) × 100.
- 3Compute 0.90 × 100 = 90%.
- 4A 90% result is excellent for many teaching-lab reactions.
Interpret an 80% yield
A synthesis gives 20 g actual product from a 25 g theoretical yield.
- 1Divide actual yield by theoretical yield: 20 ÷ 25 = 0.80.
- 2Multiply by 100 to convert the ratio to a percent.
- 3The percent yield is 80%.
- 4This falls in the good range, so the reaction worked efficiently but not quantitatively.
Check an 85% recovery
A product mass of 8.5 g is isolated from a 10 g theoretical yield.
- 1Use the same unit for both values: grams.
- 2Calculate (8.5 g / 10 g) × 100.
- 3The ratio is 0.85, so the percent yield is 85%.
- 4The interpretation is good because it is between 70% and 90%.
Quantitative 100% yield
Actual yield and theoretical yield are both 50 g.
- 1Set up percent yield = (50 g / 50 g) × 100.
- 2The ratio is exactly 1.00.
- 3Percent yield = 100%.
- 4This is the theoretical maximum for pure, completely recovered product.
Find actual yield from a known percent
A 90% yield is expected when the theoretical yield is 50 g.
- 1Rearrange to actual yield = (percent yield / 100) × theoretical yield.
- 2Substitute: actual yield = (90 / 100) × 50 g.
- 3Compute 0.90 × 50 g = 45 g.
- 4The calculator still reports the associated percent yield as 90%.
Introduction
Percent yield measures how much product a reaction actually gives compared with the maximum predicted by stoichiometry. The central equation is percent yield = (actual yield / theoretical yield) × 100. Because it is a ratio, actual and theoretical yield may be entered in grams or moles as long as both use the same unit. Use this calculator to compute the percent, classify the result, and rearrange the equation when you already know percent yield and need the matching actual or theoretical amount.
Percent yield formula
The percent-yield formula is % yield = (actual yield ÷ theoretical yield) × 100. Actual yield is the product recovered from the experiment, while theoretical yield is the stoichiometric maximum from the limiting reagent. For example, 45 g actual from 50 g theoretical gives (45/50) × 100 = 90%. If you first need formula masses for the stoichiometry, use the molar mass calculator before calculating yield.
Actual and theoretical yield must describe the same product.
Use grams with grams or moles with moles.
Multiply the ratio by 100 only after dividing actual by theoretical.
Report the percent with sensible significant figures from your measurements.
How to calculate percent yield step by step
Start with a balanced equation and determine the theoretical yield from the limiting reagent. Then measure or enter the actual isolated product amount. Divide actual by theoretical, multiply by 100, and compare the answer with expected lab performance. A 20 g actual yield from a 25 g theoretical yield is 80%. If your theoretical yield came from solution stoichiometry, the molarity calculator can help check concentration inputs.
Keep at least one extra digit during stoichiometry; round the final percent yield after the ratio is complete.
Interpreting excellent, good, moderate, and low yields
Yield categories are context dependent, but a useful classroom guide is excellent ≥90%, good from 70% to below 90%, moderate from 40% to below 70%, and low below 40%. A 90% yield suggests efficient conversion and recovery, while an 80% yield is still generally good. The formal terminology of yield and reaction quantities is aligned with IUPAC chemical terminology and standard general-chemistry treatments such as OpenStax Chemistry 2e.
These bands are practical flags, not universal grading rules. A difficult multistep synthesis can be valuable at a moderate yield.
What if percent yield is over 100%?
A pure product cannot exceed the theoretical maximum predicted by a correct limiting-reagent calculation. Therefore a percent yield above 100% usually means the product is wet, contains solvent or impurities, was weighed with contamination, or the theoretical yield was calculated incorrectly. Before reporting a value above 100%, dry the product to constant mass, verify the balanced equation, and confirm that the limiting reagent was identified correctly.
Check whether the product was fully dry.
Look for salts, mother liquor, filter paper fibers, or unreacted starting material.
Audit unit conversions between grams and moles.
Recalculate theoretical yield from the limiting reagent.
Solving for actual or theoretical yield
The same equation can be rearranged. If percent yield and theoretical yield are known, actual yield = (percent yield / 100) × theoretical yield. If actual yield and percent yield are known, theoretical yield = actual yield / (percent yield / 100). These rearrangements are useful for planning an experiment, checking notebook data, and comparing expected product amounts with recovered product.
| Known values | Unknown | Rearranged equation |
|---|---|---|
| Actual + theoretical | Percent yield | %Y = actual/theoretical × 100 |
| Percent + theoretical | Actual yield | actual = (%Y/100) × theoretical |
| Actual + percent | Theoretical yield | theoretical = actual/(%Y/100) |
Using grams or moles consistently
Percent yield has no mass unit because it compares two amounts of the same product. You can use grams for isolated mass or moles for amount of substance, but never mix them in the same ratio without conversion. For example, compare 8.5 g with 10 g, or compare 0.085 mol with 0.100 mol. Reference data from sources such as NIST Chemistry WebBook are helpful when checking formula masses or compound identities.
If the product purity is less than 100%, calculate yield using the amount of pure product rather than crude mass.
Quick Reference Card
Percent Yield — Quick Reference
Quick reference • Percent Yield Calculator
% yield = (actual ÷ theoretical) × 100Valid range: Usually 0–100% for pure product; values above 100% need purity, drying, and stoichiometry checks.
Common Values
⚠ Watch Out
- •Do not mix grams and moles in the same actual/theoretical ratio.
- •Do not report crude wet mass as pure product yield.
- •A percent yield above 100% is a warning sign, not a bonus result.
- •Theoretical yield must come from the limiting reagent and balanced equation.
Pro Tips
- →Divide actual by theoretical before multiplying by 100.
- →Dry product to constant mass before using it as actual yield.
- →Use pure-product amount if purity data are available.
- →Carry extra digits through stoichiometry and round only the final percent.
- →Compare replicate runs with percent yield rather than product mass alone.
FAQs
What is percent yield?
Percent yield is the actual product amount divided by the theoretical product amount, multiplied by 100. It shows how efficiently a reaction and workup delivered the expected product.
How do I calculate percent yield from grams?
Use grams for both actual and theoretical yield: percent yield = (actual grams / theoretical grams) × 100. For 45 g actual from 50 g theoretical, the percent yield is 90%.
Can I use moles instead of grams?
Yes. The ratio works with moles as long as actual and theoretical yield are both in moles for the same product.
What is a good percent yield?
A practical guide is excellent at 90% or higher, good from 70% to below 90%, moderate from 40% to below 70%, and low below 40%. The acceptable yield depends on reaction difficulty and purity needs.
Why can percent yield be more than 100%?
Values above 100% usually indicate wet product, impurities, contamination, weighing error, or an incorrect theoretical-yield calculation. Pure product cannot exceed the stoichiometric maximum.
How is percent yield different from actual yield?
Actual yield is the measured product amount in grams or moles. Percent yield is the normalized percentage that compares actual yield with theoretical yield.