How to calculate percentage yield

Percent yield refers to the percent ratio of actual yield to the theoretical yield. In chemistry, yield is a measure of the quantity of moles of a product formed in relation to the reactant consumed, obtained in a chemical reaction, usually expressed as a percentage. The amount of product actually made compared with the maximum calculated yield is called the percentage yield. Let us understand the percent yield formula using solved examples.

What is Percent Yield?

In chemistry, percent yield is the percent ratio of the weight of the product obtained to the theoretical yield. We calculate the percent yield by dividing the experimental yield by the theoretical yield and multiplying the result by 100 to express the final answer in %. Generally, the value of percent yield is lower than 100%, since the actual yield obtained after the reaction is often less than the theoretical value. This can be because of an incomplete reaction.

Percent yield can also be greater than 100%, meaning that more sample was recovered from the reaction than the initially predicted yield. Percent yield is always positive.

Percentage Yield Example

Let us see the decomposition reaction of magnesium oxide to understand the concept of percent yield better.

MgCO\(_3\) → MgO + CO\(_2\)

This means for 1 mole of reactant[MgCO\(_3\)], we will obtain 1 mole of product[MgO], i.e, the reactant and the product have a 1:1 mole ratio. When given the amount of reactant, we can find the theoretical yield by comparing the mole ratio. The ratio of actual yield given to this theoretical yield gives the percentage yield.

Percent Yield Formula

The percentage yield formula is calculated to be the experimental yield divided by theoretical yield multiplied by 100. If the actual and theoretical yield ​is the same, the percent yield is 100%. Usually, the percent yield is lower than 100% because the actual yield is often less than the theoretical value.

Percent Yield = (Actual Yield / Theoretical Yield) × 100 %

Formula to Calculate Percent Yield

The formula to calculate the percent yield is:

Percentage Yield = (Actual Yield / Theoretical Yield) × 100 %

where,

• Actual yield - it gives the amount of product obtained from a chemical reaction
• Theoretical yield - it gives the amount of product obtained from the stoichiometric or balanced equation, using the limiting reactant to determine the product
• Units for both actual and theoretical yield need to be the same (moles or grams)

1. Example 1: During a chemical reaction, 0.5 g of product is made. The maximum calculated yield is 1.6 g. What is the percent yield of this reaction?

   Solution:

   We know that according to Percent Yield Formula,

   Percentage yield = (Actual yield/Theoretical yield)× 100%

   = 0.5/1.6× 100%

   = 31.25%

   Therefore, the percentage yield of this reaction is 31.25%.

2. Example 2: During a chemical reaction 1.8 g of product is made. The maximum calculated yield is 3.6 g. What is the percent yield of this reaction?

   Solution:

   We know that according to Percent Yield Formula,

   Percentage yield = (Actual yield/Theoretical yield)× 100%

   = 1.8/3.6× 100%

   = 50%

   Therefore, the percentage yield of this reaction is 50%.

3. Example 3: If the percentage yield is 45% with the theoretical yield as 4g, what would the actual yield be? Calculate using the percentage yield formula.

   Solution:

   Using the percentage yield formula,

   Percentage yield = (Actual yield/Theoretical yield)× 100%

   45 = Actual yield/4 × 100

   Actual yield = 1.8

   Therefore, the actual yield is 1.8g

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FAQs on Percent Yield

Percent yield is a measure of the actual number of moles obtained for any reactant in any reaction in comparison to the predicted or theoretical yield.

What is Meant by Percent Yield Formula?

The percent yield formula is the percent ratio of actual yield to the theoretical yield. Yield is a measure of the quantity of moles of a product formed in relation to the reactant consumed, obtained in a chemical reaction, usually expressed as a percentage. The amount of product actually made compared with the maximum calculated yield is called the Percent yield. The formula is (Actual Yield / Theoretical Yield) × 100 %

What is the Formula to Calculate the Percent Yield?

The formula to calculate the percentage yield is:

Percent Yield = (Actual Yield / Theoretical Yield) × 100 %

where,

• Actual yield - it gives the amount of product obtained from a chemical reaction
• Theoretical yield - it gives the amount of product obtained from the stoichiometric or balanced equation, using the limiting reactant to determine the product
• Units for both actual and theoretical yield need to be the same (moles or grams)

Why do Use the Percent Yield Formula?

The percent yield is also used in the field of chemistry, where the percentage yield of a chemical reaction is considered very important. The formula to calculate the percentage yield is to compare the yield or the quantity of the product that is obtained.

Why is the Percent Yield not 100% When the Formula is Used?

In most cases, the percent yield is less than 100% because the actual yield is often less than the theoretical value. This is due to the incomplete or competing reactions and loss of samples during recovery.

Our percent yield calculator will help you to understand how to calculate percent yield, as well as teach you the percent yield formula and the percent yield definition. Finding the yield is an integral part of any kind of synthetic lab work as the percent yield equation turns your experimental yields into a representation of how successfully you carried out your reaction. Hopefully, after reading this page, you will have an answer to the questions "how to find percent yield?" and "what is percent yield?"

What is percent yield? The percent yield definition is that it is a measure of the effectiveness of a synthetic procedure. Wordy, right? To put it simply, percent yield tells you how well you carried out your reaction. If you were very careful with your reaction, made sure every molecule reacted and that nothing was lost when you poured the solution from one beaker to another, your percent yield would be $100\%$ (don't worry if you don't get $100\%$, this is practically impossible). If you accidentally poured your reaction mixture down the drain and lost everything, then your percent yield would be $0\%$, and if you still had a lot your solvent present with the product, your yield would be greater than $100\%$. Still confused how to find the percent yield? Check the percent yield equation below!

A percent yield of $100\%$ corresponds to the theoretical yield: discover this quantity with the theoretical yield calculator.

The percent yield can be found using the percent yield equation. It is expressed a simple percentage calculated by using the experimental yield (we learned how to calculate it with our actual yield calculator) of your product (i.e., how much of your product you made) and the theoretical mass of the product (i.e., the mass if not a single molecule was lost). The percent yield formula is:

Yp=mp,expmp,th⋅100Y_{\text{p}} =\frac{m_{\text{p},\text{exp}}}{m_{\text{p},\text{th}}}\cdot 100Yp​=mp,th​mp,exp​​⋅100

Where:

• YpY_{\text{p}}Yp​ — The percent yield;
• mp,expm_{\text{p},\text{exp}}mp,exp​ — The experimental mass of the product; and
• mp,thm_{\text{p},\text{th}}mp,th​ — The theoretical mass of the product.

The percent yield equation requires you to know two of the three variables, but it doesn't matter which two! Like any equation, it can be rearranged to find the unknown, but there's no need to worry about this when you can use our smart calculator; just enter the two known variables and find the third.

As you may have guessed from the percent yield equation above, if you want to know how to calculate the percent yield, you need two things, your experimental yield and the theoretical yield. Let's assume you have both values; how to find the percent yield?

1. First make sure the both weights have the same units (use our weight converter if you need some help 😉).
2. Take your experimental yield and divide it by the theoretical yield.
3. Multiply this value by $100$ to find the percent yield.

There you go, not too complicated right! Or you could use our percent yield calculator to calculate it easily and quickly. A note about the values obtained; a value above $100\%$ is possible but is due to solvent being present in the sample as well as your product. Dry your product thoroughly and re-weight to get the true percent yield. Also, a value of 100% is impossible to achieve; there will always be some molecules that do not react or that are left on the side of the glassware. A value of $70\%$ or higher is acceptable!

Time for some examples. Lets say you are doing a nucleophilic addition reaction, forming hydroxyacetonitrile from sodium cyanide and acetone.

Let's ignore the solvents underneath the arrow; we reacted $5\text{g}$ of acetone with $2\text{g}$ of cyanide, giving a theoretical yield of $6.54\text{g}$ of hydroxyacetonitrile. Now we know that if we carry out the experiment and get $5.58\text{g}$ of hydroxyactenitrile, what is the percent yield?

• We know our experimental yield is $5.58\text{g}$, and our theoretical yield is $6.54\text{g}$. Let's use the percent yield formula from above: Yp=mp,exp/mp,th⋅100Y_{\text{p}} =m_{\text{p},\text{exp}}/m_{\text{p},\text{th}}\cdot 100Yp​=mp,exp​/mp,th​⋅100 and fill in the fields:

Yp=5.586.54⋅100=85.3%Y_{\text{p}} = \frac{5.58}{6.54} \cdot 100 = 85.3\%Yp​=6.545.58​⋅100=85.3%

The percent yield is $85.3\%$. That was a pretty successful reaction! You should feel a bit more confident at knowing how to calculate theoretical yield now. Let's try another example to bolster that confidence.

You react $8\text{g}$ of calcium carbonate with $9\text{g}$ of acetic acid, forming $4.35\text{g}$ of acetone. Nice! Now we do this reaction, but, unfortunately, we only get $1\text{g}$ of acetone. What is the percent yield?

• Our experimental yield is $1\text{g}$, and our theoretical yield is $4.35\text{g}$. Using the percent yield formula again gives us:

Yp=14.35⋅100=22.9%Y_{\text{p}} = \frac{1}{ 4.35} \cdot 100 = 22.9\%Yp​=4.351​⋅100=22.9%

Now that's not great. Don't be upset though, there's plenty of time left in the lab session, so you try again. This time you try really, really hard to not lose any of your reaction mixture, and you end up with a yield of $5.31\text{g}$. Well, that's much better than last time, so you carry out a percent yield calculation:

Yp=5.314.35⋅100=122.1%Y_{\text{p}}= \frac{5.31}{4.35}\cdot 100 = 122.1\%Yp​=4.355.31​⋅100=122.1%

Oh no! The percent yield is over $100\%$, meaning that there is still some solvent in our product. This means we need to dry our product further, so let's do that. After re-weighing our product (this time with no solvent) we find it has a weight of $4\text{g}$. Let's calculate the percent yield:

Yp=44.35⋅100=92.0%Y_{\text{p}}= \frac{4}{4.35}\cdot 100 = 92.0\%Yp​=4.354​⋅100=92.0%

Fantastic! Now you should have a grasp on the basics of percent yield calculation, and with it have the knowledge you need to make the most out of our website. Happy calculating!