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Percent Yield Calculator

Divides the actual (experimental) yield by the theoretical yield to give percent yield, plus the amount and percentage of product lost.

When to use

You have the theoretical yield from stoichiometry and the mass or moles actually isolated, and want the reaction's percent yield.

Do not use when: You still need the theoretical yield itself (compute moles of product from the limiting reagent with moles-mass first), or you want atom economy, which compares molar masses of reagents and product rather than isolated yield.

Formula

percent_yield = 100 × actual_yield / theoretical_yield; product_lost = theoretical_yield − actual_yield

Inputs

Parameter	Type	Unit	Required	Description
`actual_yield`	number		yes	Amount of product actually obtained, in grams or moles (same unit as theoretical_yield). Range: ≥ 0
`theoretical_yield`	number		yes	Maximum amount of product predicted by stoichiometry from the limiting reagent, same unit as actual_yield. Range: > 0

Outputs

Output	Type	Unit	Description
`percent_yield`	number	%	100 × actual / theoretical.
`yield_fraction`	number		actual / theoretical.
`product_lost`	number		theoretical − actual, in the input unit.
`percent_lost`	number	%	100 − percent_yield.

Example

4.5 g obtained of 5.0 g theoretical: {"actual_yield":4.5,"theoretical_yield":5} → {"percent_yield":90,"yield_fraction":0.9,"product_lost":0.5,"percent_lost":10}

12.3 g obtained of 15.0 g theoretical: {"actual_yield":12.3,"theoretical_yield":15} → {"percent_yield":82,"product_lost":2.7}

GET https://tttkmbb.com/api/v1/calculate/percent-yield?actual_yield=4.5&theoretical_yield=5

Machine access

API: GET https://tttkmbb.com/api/v1/calculate/percent-yield (query parameters) or POST with a JSON body {"inputs": {...}}
Schema: https://tttkmbb.com/api/v1/calculators/percent-yield · Markdown: https://tttkmbb.com/chemistry/percent-yield.md · JSON definition: https://tttkmbb.com/chemistry/percent-yield.json
MCP: server https://tttkmbb.com/mcp, tool run_calculator with calculator_id="percent-yield"
OpenAPI operationId: calculate_percent_yield
Freshness: static. Authentication: none. Rate limit: fair use (see rate limits).

Sources

OpenStax Chemistry 2e – 4.4 Reaction Yields (textbook)
Wikipedia – Yield (chemistry) (reference)

FAQ

Can percent yield exceed 100%?

Not for a pure, dry product. A value above 100% indicates residual solvent, impurities or a weighing error; the calculator reports it with a note.

Should I use grams or moles?

Either, as long as both yields use the same unit for the same product; the ratio is identical.

Related calculators

Moles to Grams Calculator — Convert moles of product from stoichiometry into the theoretical mass.
Molar Mass Calculator — Molar mass of the product for the mass conversion.
Percentage Calculator — General percentage arithmetic.