Stoichiometry and Yield Guide

This page is a hub, not a calculator: it lays out the full sequence a stoichiometry-to-percent-yield problem follows, and links to a dedicated calculator or guide for every stage of that sequence. Each section below covers one stage in a few sentences, explains what that stage answers and why it comes where it does, and then links to the page built for that specific task.

Use the table near the end as a quick-reference index if you already know which stage you need, or read straight through if you are working a problem for the first time and want the full order of operations from a balanced equation to a rated percent yield.

Every calculation on this site depends on one starting point: a balanced chemical equation. The coefficients in a balanced equation set the mole ratios that every later step, from mass conversions to yield percentages, is built on. An equation that is not balanced will carry a wrong ratio through the entire chain and produce a wrong answer at the end, even if every other calculation along the way is done correctly.

This is true whether the reaction is a simple synthesis or a multi-step organic sequence: the ratio of coefficients never changes once the equation is written correctly. Start by learning how to balance equations by inspection and by algebraic methods on the balanced equation guide, then move on to converting the masses you would actually weigh out in a lab into moles.

Chemical equations are written in moles, but a lab balance reports grams. The molar mass of a compound, its mass in grams per mole, is the conversion factor that links the two. Once you can move from a measured mass to a mole count, you can use the balanced equation's coefficients directly, without guessing at what a given mass actually represents in terms of particles.

Use the molar mass calculator to find the mass of one mole of any compound from its chemical formula, and the grams-to-moles converter to turn a measured mass into the mole count a stoichiometry problem needs. These two conversions come up in almost every problem on this site, so it pays to be comfortable with them before moving further.

The coefficients of a balanced equation give a fixed ratio of moles between any two substances in the reaction. That ratio, called the mole ratio, is the tool that lets you take a known number of moles of one reactant and find the matching number of moles of a product or of another reactant, without needing any additional data.

Practice reading and applying mole ratios directly from a balanced equation with the mole ratio calculator, then combine mole ratios with molar mass conversions to work full mass-to-mass problems with the stoichiometry calculator, which carries a starting mass all the way through to a finished product mass in one pass.

Real reactions are rarely run with reactants in an exact stoichiometric ratio. When two starting amounts are given, one reactant runs out first and stops the reaction; the other is left over. The reactant that runs out first is called the limiting reactant, and it alone determines how much product can form, regardless of how much of the other reactant is sitting in the flask.

Find which reactant limits the reaction with the limiting reactant calculator, then find how much of the other reactant remains unreacted with the excess reactant calculator. If the reaction stops before every bit of the limiting reactant is consumed, which happens with slow or reversible reactions, the reaction completion calculator shows what fraction of the limiting reactant actually reacted.

Once the limiting reactant is known, its mole ratio to the product gives the maximum mass of product the reaction can produce under perfect conditions, with no losses and no side reactions. That maximum is the theoretical yield, and it is the denominator in every percent yield calculation that follows.

Calculate a theoretical yield directly with the theoretical yield calculator, then read the percent yield formula page and the percent yield equation page for the full derivation and its algebraic rearrangements. The homepage calculator combines all three quantities, solving for percent yield, theoretical yield, or actual yield from whichever two values you already have.

Sometimes a lab report or a textbook problem gives a percent yield and a theoretical yield but not the actual mass of product recovered. Rearranging the percent yield formula to isolate actual yield answers that question directly, without repeating the full stoichiometry calculation from the balanced equation onward.

Use the actual yield calculator to solve for the mass actually produced when the percent yield and theoretical yield are already known, which is common when checking a claimed result against a set of raw stoichiometry data.

Several other percentages describe a reaction or a purification, and it is easy to mix them up with percent yield. Reaction efficiency compares how a reaction performed against an ideal outcome; percent recovery compares the mass of a compound recovered after a purification step, such as recrystallization, to the mass that went into that step; percent purity describes how much of a recovered sample is the desired compound versus leftover impurities; percent error compares an experimental result to an accepted or literature value; and percent loss tracks how much material was lost during handling, transfer, or purification.

Each of these has a distinct denominator and answers a distinct question, even though the arithmetic often looks similar on the surface. Compare them directly with the reaction efficiency calculator, the percent recovery calculator, the percent purity calculator, the percent error calculator, and the percent loss calculator.

A percent yield below 100% is normal and expected in almost every real reaction, but a yield far below what is typical for a given reaction type usually traces back to one or two identifiable causes: an incomplete reaction, loss of product during transfer or filtration, a side reaction competing for the limiting reactant, or a measurement error in one of the original masses.

Work through the eight most common causes of low yield on the lab errors page before assuming a low result is simply a mistake in the calculation itself.

Reading through a calculation once is not the same as being able to run it from a blank page under exam or lab conditions. Work through fully solved problems first to see each decision explained, then attempt problems without the solution visible, then repeat the sequence with a fresh set of numbers until the steps come without hesitation.

Start with the eight worked percent yield examples, move to the ten practice problems, and finish with the fifteen printable tiered worksheets, which range from introductory single-step conversions to multi-step problems that involve finding a limiting reactant before the yield calculation even begins.

The table below lists every calculator and guide on this site in the order a full stoichiometry-to-yield problem is normally worked, from balancing an equation to diagnosing a disappointing result. Use it as a quick lookup once you already know which stage of the sequence you need.