Actual Yield Calculator
Actual yield is the mass of product you physically isolate and weigh, not a predicted number. To estimate it beforehand, rearrange the percent yield formula: actual yield equals percent yield divided by 100, times theoretical yield. A step expected to run at 70% yield from a 15 g theoretical yield should produce about 10.5 g of product.
What Actual Yield Measures
Actual yield is the mass of product you recover after the reaction is complete, once it has been isolated, purified where needed, dried, and placed on a balance. It is an experimental result, not a calculation: you obtain it by running the synthesis, not by working through mole ratios on paper. This makes it fundamentally different from theoretical yield, which is the maximum mass predicted from the limiting reagent using stoichiometry; see how theoretical yield is calculated from grams to moles and back to grams for that method.
Percent yield connects the two figures as a ratio, actual divided by theoretical, times 100, covered in full on the percent yield calculator home page. The calculator above runs that relationship in reverse. Instead of starting with a measured actual yield, you enter a target or expected percent yield along with a theoretical yield, and it solves for the actual mass in grams that percentage corresponds to.
The Rearranged Formula
The standard percent yield formula is percent yield equals (actual yield divided by theoretical yield), times 100. Solving that equation for actual yield instead of percent yield gives: actual yield = (percent yield / 100) x theoretical yield. The full derivation and its other rearrangements, including solving for theoretical yield, are worked out on the percent yield formula page.
This particular rearrangement is useful whenever you know or can estimate a percent yield before you have a real measurement in hand. A lab manual or a published procedure often states an expected percent yield for a given step, for instance 65 to 75%. Plugging that figure and your calculated theoretical yield into the rearranged formula tells you roughly what mass should land on the balance, so you have a reference point before the reaction is even run, and can flag a result that is unexpectedly low or suspiciously high once it is finished.
Three Worked Examples
Example 1. Percent yield is 70% and theoretical yield is 15 g. Actual yield = (70 / 100) x 15 g = 0.70 x 15 g = 10.5 g.
Example 2. Percent yield is 92% and theoretical yield is 8.40 g. Actual yield = (92 / 100) x 8.40 g = 0.92 x 8.40 g = 7.728 g. On a balance reading to three decimal places, that would be recorded as 7.728 g.
Example 3. Percent yield is 84.5% and theoretical yield is 23.6 g. Actual yield = (84.5 / 100) x 23.6 g = 0.845 x 23.6 g = 19.942 g. Non-round percentages like 84.5% routinely produce actual yields with several decimal digits, which is expected and not a sign of an arithmetic mistake.
Sanity-Check Table
For a fixed theoretical yield of 20.0 g, the table below shows the actual yield you should expect across common percent-yield bands. Use it to check that a computed result falls in a reasonable range before you accept it.
| Percent yield | Actual yield |
|---|---|
| 50% | 10.0 g |
| 70% | 14.0 g |
| 80% | 16.0 g |
| 90% | 18.0 g |
| 100% | 20.0 g |
If your own numbers scale similarly, for example roughly three-quarters of the theoretical yield at a percent yield near 75%, the result is likely correct. A computed actual yield larger than the theoretical yield figure at the 100% row signals an error in the inputs, not a real result.
Why Actual Yield Rarely Reaches 100%
Actual yield is virtually always less than or equal to theoretical yield in a real experiment, because theoretical yield assumes every bit of limiting reagent converts cleanly to product with no side reactions, no incomplete reactions, and no material lost during transfer, filtration, or drying. Real reactions fall short of that ideal for one or more of those reasons, which is exactly what percent yield quantifies. The general reasoning behind that ceiling, along with the core percent yield definition, is covered on the home page; the specific causes of a lower than expected result are broken down further on common lab errors that reduce yield.
Getting an Honest Actual Yield in the Lab
An actual yield measurement is only as good as the weighing technique behind it. Dry the isolated solid to constant mass, meaning you weigh it, dry it further, and weigh it again until the reading stops changing; a still-wet solid weighs more than the dry product and inflates the actual yield artificially. Tare the balance with the exact container you will weigh into, whether that is a piece of filter paper, a vial, or a weighing boat, so the container mass is not counted as product.
Avoid weighing a solid while it is still wet with mother liquor or wash solvent, since residual liquid can add a meaningful fraction of a gram on small-scale reactions. Account for transfer losses too: product left behind on a stir rod, filter paper, or the sides of a flask never reaches the balance, which is one of the practical reasons actual yield sits below the theoretical yield ceiling and why comparing the result against your reaction efficiency classification is a useful check on lab technique.
Frequently asked questions
How do I find actual yield from percent yield?
Multiply the percent yield, expressed as a decimal, by the theoretical yield: actual yield = (percent yield / 100) x theoretical yield. For instance, at 88% yield with a 12.0 g theoretical yield, actual yield = 0.88 x 12.0 g = 10.56 g. This is the same relationship the calculator above solves automatically once you enter both values.
What if I only have the actual yield and want the percentage?
Rearrange the formula the other way: percent yield = (actual yield / theoretical yield) x 100. If you measured 9.2 g against a 12.0 g theoretical yield, percent yield = (9.2 / 12.0) x 100 = 76.7%. The percent yield mode of the home page calculator handles this direction directly if you enter actual and theoretical yield instead.
Can actual yield exceed theoretical yield?
No, not in a chemically real sense, since theoretical yield already represents the maximum mass possible from the limiting reagent. A measured actual yield above theoretical yield, giving over 100% yield, almost always means the isolated solid still contains moisture, solvent, or an unreacted impurity adding extra mass that is not the intended product.
Why is my actual yield a decimal with lots of digits?
Because the rearranged formula rarely produces round numbers unless the percent yield or theoretical yield happens to be a tidy multiple. For example, 84.5% of 23.6 g works out to 19.942 g. This is normal; round the final figure to match the precision of the balance you are reporting from, typically two to four decimal places.
Does actual yield need to be dried first?
Yes, a solid product should be dried to constant mass before it is weighed as the actual yield. Residual solvent or water trapped in the solid adds mass that is not part of the product itself, so weighing it wet gives an actual yield, and therefore a percent yield, that reads higher than the true chemical result.
What's the difference between actual yield and percent recovery?
Actual yield describes the mass of new product obtained from a synthesis reaction, compared against a theoretical yield calculated from stoichiometry. Percent recovery instead describes a purification step, comparing the mass of a substance recovered after recrystallization or another cleanup process to the mass of the impure sample you started that step with. See <a href="/recovery/">percent recovery</a> for that calculation.
How precise should my balance be?
For most undergraduate-scale reactions, a balance reading to two or three decimal places, such as 0.01 g or 0.001 g, is precise enough to give a meaningful actual yield. Smaller-scale reactions producing a fraction of a gram need an analytical balance reading to 0.0001 g, since rounding error becomes a larger fraction of the total mass as the sample size shrinks.
What if my actual yield is zero?
An actual yield of zero means no isolable product was recovered, giving a 0% yield. This usually points to a reaction that did not proceed, a product lost entirely during workup or filtration, or a misidentified limiting reagent that changes what the theoretical yield should have been. See <a href="/lab-errors/">common lab errors</a> for the usual causes.
Can actual yield be negative?
No, mass cannot be negative, so a real actual yield is always zero or a positive number. If a rearranged-formula calculation returns a negative value, the cause is an input error, most often a negative percent yield typed by mistake or a theoretical yield entered with the wrong sign, not an actual physical result.
How do lab errors affect actual yield?
Lab errors almost always push actual yield down, never up, relative to the theoretical yield ceiling. Common causes include product left behind during transfer, incomplete reactions that stop before full conversion, competing side reactions consuming the limiting reagent, and mechanical losses during filtration. The <a href="/lab-errors/">lab errors page</a> covers eight specific causes of a low actual yield in detail.