Calculate
Formula and method
Convert each mass to moles using the site’s Molecular Weight atomic-weight table. Divide all moles by the smallest. Test multipliers 1–12; accept the first for which each scaled ratio is within 0.025 × multiplier of a positive integer, with every subscript at most 12. Otherwise show no reliable small ratio. Percentages must total within 1 percentage point of 100.
Worked example
Approximately 27.29% carbon and 72.71% oxygen reduce to an approximate 1:2 mole ratio, giving CO₂. Subscript 1 is omitted.
Assumptions and limitations
Rounded or noisy composition data may not resolve within the supported tolerance. This derives an empirical ratio only, not a molecular formula or compound identity.
Frequently asked question
Why might no formula appear?
The entered values may be too imprecise or not close to a small whole-number ratio under the documented tolerance.
Methodology source
OpenStax Chemistry 2e: Determining Empirical and Molecular Formulas. Reference, not endorsement.