What is the percent yield formula?

Percent yield = actual yield ÷ theoretical yield × 100. The actual yield is the mass or moles you really isolated; the theoretical yield is the most the balanced equation could give from your limiting reagent. For example, if a reaction could in theory make 10 g of product and you recovered 8 g, the percent yield is 8 ÷ 10 × 100 = 80%. The two amounts must be in the same unit so the ratio cancels it.

What is the difference between actual and theoretical yield?

Theoretical yield is the maximum, calculated from stoichiometry and the limiting reagent assuming the reaction goes perfectly to completion. Actual yield is what you physically weigh after workup. Actual is almost always smaller. If your limiting reagent gives a theoretical 0.050 mol of product but you isolate 0.041 mol, the actual yield is 0.041 mol and the percent yield is 82%. Compute theoretical yield first with a molar mass calculator, then divide.

Why is percent yield usually less than 100%?

Three reasons cost you product. Mechanical loss: material sticks to glassware, stays in the filter cake, or is lost when you decant and wash. Side reactions: some reagent makes a byproduct instead of your target. Incomplete or reversible reactions: an equilibrium that lies short of completion leaves starting material behind. A clean small-molecule synthesis might hit 90%, while a multi-step total synthesis can drop into single digits per step.

What does a percent yield over 100% mean?

A yield above 100% is physically impossible for real product, so it flags a measurement problem rather than a triumph. The usual culprit is mass that is not pure product: residual solvent, water from a sample that was not dried to constant weight, or unreacted reagent and inorganic salts carried through. Dry the product fully, reweigh, and the number should fall back below 100%. It can also mean the theoretical yield was underestimated.

How do I calculate the theoretical yield?

Find the limiting reagent, convert its mass to moles with a molar mass calculator, apply the mole ratio from the balanced equation, then convert product moles back to grams. Example: 5.0 g of a reagent with molar mass 100 g/mol is 0.050 mol; a 1:1 ratio gives 0.050 mol of product, and at product molar mass 120 g/mol that is 6.0 g theoretical. Feed that 6.0 g here as the theoretical yield.

Can this tool back-solve the theoretical yield from a percent?

Yes. Switch the solve-for control to theoretical yield, enter the actual yield you isolated and the percent yield you achieved, and it computes the maximum the reaction could have given: theoretical = actual ÷ (percent ÷ 100). If you recovered 8 g at a reported 80% yield, the theoretical yield was 8 ÷ 0.80 = 10 g. A percent of zero cannot be back-solved, so the tool shows a hint instead of dividing by zero.

Finish an organic chemistry lab report

You ran a synthesis, dried the product to constant weight and put it on the balance: 1.84 g. Your prelab said the theoretical yield was 2.30 g. Drop both numbers in, read 80%, and paste the result straight into the results section. The note reminds you to attribute the missing 20% to recrystallization loss and a small amount of side product, which is exactly the discussion your TA is looking for.

Plan how much starting material to weigh out

You need 5.0 g of final product but you know this reaction only runs at about 65% on your hands. Switch to solve for theoretical yield, enter 5.0 g actual and 65%, and the tool tells you the reaction has to be designed for 7.7 g theoretical. Now scale the limiting reagent up to that target instead of coming up short and repeating the synthesis.

Grade or check a batch of student calculations

A teacher collecting lab reports can sanity-check each percent yield in seconds: type the student's actual and theoretical figures, see whether the percent they wrote matches. Any report claiming over 100% gets flagged by the tool's note, which is the teachable moment about drying the product before weighing.

Compare two routes to the same molecule

Route A gives 6.2 g from a 8.0 g theoretical; route B gives 4.1 g from a 4.5 g theoretical. Per-step the percentages are 78% versus 91%. Computing each here puts the two side by side so you choose the higher-yielding, less wasteful path rather than guessing from the raw masses, which favor the bigger batch by accident.

Percent Yield Calculator — Actual, Theoretical and Reaction Yield

actual ÷ theoretical × 100 — solve for percent, actual or theoretical yield, grams or moles, with a plain-English read on why it is below or above 100% — browser-only

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Solve for:

Unit:

Actual yield (g)

Theoretical yield (g)

Result · Percent yield

80%

About this number

Yields under 100% are normal. Product is lost on transfer, filtration and recrystallization, and side reactions and equilibrium leave some starting material unconverted.

percent yield = actual ÷ theoretical × 100

What this tool does

Free percent yield calculator for organic and general chemistry. Percent yield measures how much product a reaction actually gave compared with the maximum the stoichiometry allowed: percent yield = actual yield ÷ theoretical yield × 100. Enter any two of the three quantities — actual yield, theoretical yield or percent — and the tool solves for the third. Actual and theoretical share one unit, grams or moles, and the ratio cancels it so the percent is unitless either way. Most real reactions land well under 100% because product is lost on transfer, filtration and recrystallization, and side reactions or equilibrium leave some material unconverted. A figure above 100% is a warning that the product is still impure or wet rather than a great result. Everything runs in your browser with one-click copy and a shareable link that reopens the same numbers. 100% client-side, nothing uploaded.

Tool details

Input: Numbers; The page exposes text boxes, numeric controls, file pickers, or structured inputs depending on the tool.
Output: Live result + Copy; The result area focuses on usable output, with copy, download, or preview actions when supported.
Privacy: Browser-side processing; The main tool logic does not call an external API, so inputs normally stay in the current tab.
Save / share: Shareable URL state; Key settings are encoded in the URL so another person can reopen the same setup.
Performance budget: Initial JS <= 9 KB; No WASM budget is declared, keeping the tool quick to open on mobile.
Best fit: Calculator · Student; Category and role tags drive related tools, internal links, and quick fit checks.

How to use

1. Input

Paste or drop your content into the tool panel.
2. Process

Click the button. All processing is local in your browser.
3. Copy / Download

Copy the result or download to disk in one click.

How Percent Yield Calculator fits into your work

Use it for fast estimates, comparisons, and planning numbers before you make the final call.

Calculation jobs

Getting a realistic range before a purchase, plan, workout, or schedule decision.
Comparing scenarios by changing one input at a time.
Turning rough assumptions into a number you can discuss.

Calculation checks

Double-check units, dates, rates, and rounding assumptions.
Treat health, finance, tax, and legal outputs as planning aids, not professional advice.
Save the inputs that produced an important result so you can reproduce it later.

Good next steps

These links move the current task into a more complete workflow.

Real-world use cases

Finish an organic chemistry lab report
You ran a synthesis, dried the product to constant weight and put it on the balance: 1.84 g. Your prelab said the theoretical yield was 2.30 g. Drop both numbers in, read 80%, and paste the result straight into the results section. The note reminds you to attribute the missing 20% to recrystallization loss and a small amount of side product, which is exactly the discussion your TA is looking for.
Plan how much starting material to weigh out
You need 5.0 g of final product but you know this reaction only runs at about 65% on your hands. Switch to solve for theoretical yield, enter 5.0 g actual and 65%, and the tool tells you the reaction has to be designed for 7.7 g theoretical. Now scale the limiting reagent up to that target instead of coming up short and repeating the synthesis.
Grade or check a batch of student calculations
A teacher collecting lab reports can sanity-check each percent yield in seconds: type the student's actual and theoretical figures, see whether the percent they wrote matches. Any report claiming over 100% gets flagged by the tool's note, which is the teachable moment about drying the product before weighing.
Compare two routes to the same molecule
Route A gives 6.2 g from a 8.0 g theoretical; route B gives 4.1 g from a 4.5 g theoretical. Per-step the percentages are 78% versus 91%. Computing each here puts the two side by side so you choose the higher-yielding, less wasteful path rather than guessing from the raw masses, which favor the bigger batch by accident.

Common pitfalls

Mixing units between actual and theoretical yield. If one is in grams and the other in moles the ratio is meaningless. Convert both to the same unit first — use a molar mass calculator to go between grams and moles — then divide.
Using a reagent that is not the limiting one to compute the theoretical yield. The theoretical maximum is set by whichever reactant runs out first, not by the one you happened to weigh. Identify the limiting reagent before you calculate, or your percent will be wrong.
Weighing the product before it is dry and then trusting a yield over 100%. Residual solvent and water inflate the mass. Dry to constant weight, reweigh, and recompute. A number above 100% is a drying problem, not a record-breaking reaction.

Privacy

Every step — the percent formula, the back-solve for actual or theoretical yield, and the unit handling — is plain JavaScript that runs in your browser tab. No mass, mole count or percentage ever leaves the page, and nothing you type is logged. The one caveat: the shareable URL encodes your two inputs, the solve mode and the unit in the query string, so a link pasted into chat will record those values in the recipient server's access log. For unpublished lab data, use the copy button and paste the text rather than sharing the URL.

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Percent Yield Calculator — Actual, Theoretical and Reaction Yield

About this number

What this tool does

Tool details

How to use

1. Input

2. Process

3. Copy / Download

How Percent Yield Calculator fits into your work

Calculation jobs

Calculation checks

Good next steps

Real-world use cases

Finish an organic chemistry lab report

Plan how much starting material to weigh out

Grade or check a batch of student calculations

Compare two routes to the same molecule

Common pitfalls

Privacy

FAQ

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