Chemistry tools,
instantly.

Quemist is a working reference for people doing chemistry — not a course and not a textbook. Three kinds of page live here.

Calculators for the arithmetic that sits between a procedure and a result: molar mass from a formula, molarity and dilution, stoichiometry and limiting reagent, the gas laws, pH and buffers, calorimetry, half-life, electron configuration. Each one shows every intermediate step, because the intermediate number is usually the one you need to check.

Unit converters for the units chemistry insists on keeping in circulation — pressure in torr, mmHg, atm and bar; concentration in molar, ppm and percent w/v; energy in joules, calories and electronvolts. Each converter page also sets out where its factor comes from and whether that factor is exact or measured.

Reference pages for all 118 elements and several hundred compounds, plus the tables you look up rather than memorise: solubility rules, the activity series, standard reduction potentials, common ions, electronegativity.

Everything runs in your browser. Nothing you type is sent anywhere, there is no account, and no calculation is stored.

Inputs live in the page URL, so a worked example is just a link. You can bookmark a dilution you run every week, or paste one to a student, and it opens with the numbers already in place.

Every result comes with its working shown. A molar mass is not much use on its own if you have mistyped a subscript — seeing the per-element breakdown is how you catch it. The same applies to a gas-law answer that quietly needed a temperature in kelvin.

New to the site? There are short starting points for students, teachers, researchers and lab technicians, plus around fifty how-to guides that walk through a calculation end to end.

Atomic masses are IUPAC standard atomic weights — the conventional values, not isotope-specific ones. Molar masses computed from them inherit that uncertainty, so a molar mass is never exact at any number of decimal places.

Conversion factors are labelled on each page as exact by definition or as measured, because the distinction decides how many digits are worth keeping. One atmosphere is exactly 101325 pascals and always will be; the mass of a mole of glucose is a measurement that can be revised.

Quemist is an educational reference, and it is free because the pages carry advertising. Check anything consequential against a primary source before you rely on it — the about page explains the scope, and the disclaimer sets out the limits.