How this calculation works
Expand neutral molecular formulas and verify each element balances across all entered species. Apply reactant purity, compare stoichiometric extents and use the limiting extent for products and excess-reactant leftovers.
Available reaction extent = min(reactant pure moles / stoichiometric coefficient); product mass = extent × product coefficient × molar massA worked example
For 2 H2 + O2 → 2 H2O, 4.032 g H2 and 31.998 g O2 are stoichiometric at the listed conventional weights. The theoretical water mass is 36.03 g; a measured 30 g yield is about 83.264%.
Good to know
Stoichiometric bound, not synthesis guidance, selectivity or safety. Neutral formulas only, no charge balancing or isotope masses. All balanced products must be listed; actual mass concerns the first product.
Reference: OpenStax: limiting reactants and reaction yields (opens in a new tab) ↗
Balance the complete reaction first
Every entered element must have the same total atom count on both sides using the supplied whole coefficients. Omitting a byproduct can make an otherwise familiar reaction unbalanced.
Formula parsing and balance do not establish that a reaction occurs or proceeds selectively. They only make the stoichiometric accounting internally consistent.
Compare reaction extents rather than raw masses
A large mass can still be limiting when its molar mass or required coefficient is large. Divide available pure moles by the corresponding coefficient before comparing reagents.
Purity removes inert mass from availability. Leftover values describe pure unconsumed reactant under the ideal conversion model, not a tested composition of a real reaction mixture.
Separate theoretical output from measured yield
Theoretical product is the upper bound from the limiting extent and the written stoichiometry. Measured product mass is a separate observation used for percent yield.
A result over 100% is shown rather than clipped. It can reflect measurement, moisture, impurities or a model mismatch and is not silently treated as physical confirmation of extra product.
Use the result with the next measurement
The empirical and molecular formula candidate calculator infers composition ratios from measurements. This yield calculation instead requires supplied neutral formulas and a separately balanced reaction.
Stoichiometric bound, not synthesis guidance, selectivity or safety. Neutral formulas only, no charge balancing or isotope masses. All balanced products must be listed; actual mass concerns the first product.
A few questions, answered
Must I include all products?
Yes, the element-balance check uses the complete written reaction.
Does this balance charged redox equations?
No, only entered neutral-formula element balance is checked.
Are yields above 100% hidden?
No, the entered measurement is retained.