About | Quemist

Quemist is a chemistry reference site. Calculators for the arithmetic you keep redoing (molar mass, pH, dilutions, gas laws, stoichiometry), unit converters for the awkward chemistry units, and reference pages for the 118 elements and the few hundred compounds that show up most often in coursework and the lab.

It is a reference, not a course. There is no curriculum, no lesson sequence, no assessment, and no attempt to teach a concept from first principles. The assumption behind every page is that you already know what you are trying to calculate and want the arithmetic done visibly, or that you know what value you need and want to find it without wading through an encyclopaedia article first.

Who it's for

Four kinds of reader, roughly. Students working through general or organic chemistry, who need the intermediate steps because the intermediate steps are what gets marked. Teachers, who get more out of the fact that a filled-in calculator is a shareable URL than out of any individual tool. Researchers, who mostly want unit conversions whose provenance is stated. And technicians, whose daily arithmetic is dilutions and solution prep and who benefit from being able to bookmark a calculation they repeat. There are short orientation pages for students, teachers, researchers and lab technicians that say what to reach for first.

How it's built

Every page is plain HTML generated ahead of time. There is no application server, no database and no rendering step that happens while you wait. The calculators are small self-contained widgets that load only on the pages that need them, which is why a reference page — an element, a compound, a table — carries no interactive code at all.

The arithmetic happens in your browser. Nothing you type into a calculator is transmitted anywhere, nothing is stored, and there is no account to create. Inputs are held in the page URL instead of on a server, which has the useful side effect that a completed calculation is just a link: bookmark it, paste it into a problem set, or send it to someone and it opens with your numbers in place.

Every calculation function is a plain function with test coverage, checked against worked textbook problems rather than against itself. Every calculator prints its intermediate steps, which is a design decision rather than a feature: a result you cannot audit is a result you have to trust, and a molar mass computed from a mistyped subscript looks exactly as confident as a correct one.

Accuracy standards

Atomic masses follow IUPAC standard atomic weights — the conventional values used across general chemistry, not isotope-specific masses. Molar masses are summed from those weights at full precision rather than from pre-rounded figures, so a value here can differ in the third decimal place from a textbook that rounds first.

Conversion factors are labelled on each converter page as exact by definition or as measured, because the distinction decides how many digits are worth keeping. One standard atmosphere is exactly 101325 pascals and will not be revised. Zero Celsius is exactly 273.15 kelvin. A molar mass, by contrast, is a sum of measured quantities and is not exact at any number of decimal places — it inherits whatever uncertainty sits in the standard atomic weights behind it. Reference tables name their sources where the provenance matters.

What it doesn't do

There is no safety data here: no hazard classifications, no exposure or disposal information, no handling guidance, no regulatory limits. Those belong to the Safety Data Sheet for the specific material you have and to whatever procedures your institution runs. Nothing on the site is validated for use in a controlled, clinical or regulated process, and it should not be cited in published work — cite the IUPAC, NIST or CODATA compilation the value originally came from. The disclaimer and the Terms of Service set out the limits in full.

Corrections

A wrong atomic mass is a real bug, and it propagates: every molar mass, percent composition and stoichiometry result that touches that element is wrong with it. Reports of incorrect values are the most useful thing anyone sends. The contact page explains what to include so a report can be checked against the reference quickly.

Why it's free