About Chemkit

Chemkit exists because most free chemistry calculators on the open web are either wrong, ambiguous about their units, or ad-plastered to the point of unusability. Every tool here is unit-tested against a canonical textbook worked example before it ships, and every physical constant cites its source.

Our approach

• Chemistry correctness is the first priority. We never guess a constant, pKa, or molecular weight. Every value carries an inline source citation.
• Every calculator shows the equation it uses and a worked example, so you can verify the tool matches your expectation.
• Significant figures propagate from your inputs to the displayed answer. You can override.
• Rounding happens only at display time — intermediate math is full precision.
• Every tool is keyboard-navigable, screen-reader-labeled, and meets WCAG AA color contrast.

Sources & citations

The following authorities are the primary sources for the values used across the site:

• Physical constants: CODATA 2018 recommended values, published by NIST.
• Atomic weights: IUPAC 2021 recommended atomic weights (Prohaska et al., 2022).
• Thermodynamic data: NIST WebBook and CRC Handbook of Chemistry and Physics, current edition.
• Acid/base constants: CRC Handbook, cross-checked against Bordwell pKa tables where relevant.
• Nomenclature and definitions: IUPAC Gold Book.

Individual calculators cite the specific textbook or reference that a worked example comes from, in a comment in the source code and — where appropriate — on the tool's page itself.

Corrections

Found a bug or a value that disagrees with a primary source? Please tell us. See the contact page.