TAHA Engineering Toolsby TAHA Knowledge Lab

Chemical Engineering

Reaction Yield & Conversion Calculator

Percent yield, actual or theoretical yield, and reactant conversion, in mass or moles — and how yield differs from conversion and selectivity.

Inputs

Calculate from
A reactor with a feed arrow in and three arrows out: unreacted reactant, desired product and by-products.reactant fedn(fed)Reactorunreacteddesired productby-productsX = converted ÷ fed · Yield = X × SS = desired ÷ converted (stoichiometric basis)
Conversion X is the share of the feed that reacted. Selectivity S is the share of the reacted feed that became the desired product. Yield is the share of the maximum possible product actually obtained: Yield = X × S. High conversion does not mean high yield. Diagram not to scale.

The amount of pure, dry product actually obtained.

The maximum amount from the limiting reagent (see the Stoichiometry & Limiting Reagent calculator).

Result

Percent yield
80.26%
Shortfall (theoretical − actual)
11.12
Working
% yield = actual ÷ theoretical × 100 = 45.2 g ÷ 56.32 g × 100 = 80.2557%

The percent yield is 80.26%.

  • Both quantities must be for the same product and on the same basis (both masses or both moles of that product).

Educational estimate — check the assumptions below.

About this calculator

Percent yield compares the amount of product you actually obtained with the maximum possible amount (the theoretical yield, set by the limiting reagent). Conversion is a different measure: the fraction of a reactant that was used up, whatever it turned into.

The two are not interchangeable. A reaction can convert 90% of its feed but give a low yield if much of it forms by-products. The link between them is the selectivity — the fraction of the converted reactant that became the desired product. This calculator works out yield, actual or theoretical yield, and conversion, in mass or moles. For production scrap and first-pass yield of manufactured parts, use the Scrap Rate & Yield calculator instead.

Formula

% yield = actual ÷ theoretical × 100    actual = theoretical × % yield ÷ 100    theoretical = actual × 100 ÷ % yield

Conversion X = (nfed − nunreacted) ÷ nfed × 100    Yield = X × S (both on a mole basis, with stoichiometry)

Actual and theoretical yield are of the same product in the same unit (mass or moles). Conversion is for one reactant (mass or moles give the same result). S = selectivity: moles of desired product formed per mole of reactant converted, multiplied by the stoichiometric ratio so that S = 1 when nothing else forms.

Worked example

  • Theoretical NH₃ 56.32 g, actual 45.20 g: % yield = 45.20 ÷ 56.32 × 100 = 80.26%.
  • 100 g of reactant fed, 25 g left: conversion = (100 − 25) ÷ 100 = 75%.
  • Yield vs conversion: if X = 75% and selectivity S = 90%, yield = 0.75 × 0.90 = 67.5% — lower than the conversion.

Assumptions and limitations

  • Actual and theoretical yields refer to the same pure product, on the same basis (both masses or both moles).
  • The theoretical yield comes from the limiting reagent and the balanced equation.
  • Conversion is for one reactant. In a reaction with several reactants each has its own conversion; the limiting reagent is normally used.
  • Yield, conversion and selectivity have several definitions in industry (per pass or overall, mole or mass basis). State which you use.
  • A calculation tool only, not chemical handling advice.

References

  • Fogler, H. S., Elements of Chemical Reaction Engineering — conversion, selectivity and yield.
  • IUPAC, Compendium of Chemical Terminology (the “Gold Book”).