Terms of use

Last updated 4 August 2026.

Using this site means accepting the terms below. They are short because the site is short: a set of chemistry calculators and reference pages, free to use, with no account and nothing to buy.

What the site is for

This is an educational reference. The calculators implement standard stoichiometric relationships and show their working so you can follow and check every step. Every result is a restatement of the numbers you entered under the formula shown on the page.

Verify any result that matters against your own balanced equation before acting on it. A calculator cannot know whether your equation is balanced correctly, whether the reagent you called limiting really is, or whether the mass you weighed was dry. Those judgements stay with you.

No warranty

The site is provided as is. It is built carefully and every calculation is covered by an automated test suite, but no guarantee is given that it is free of errors or suitable for any particular purpose. To the extent permitted by law, no liability is accepted for loss arising from use of the site or reliance on its output, including loss of materials, time or marks.

If you find an error, reporting it through the contact page is genuinely useful and it gets fixed.

Laboratory safety is outside the scope

Nothing here is guidance on handling chemicals. The site calculates quantities and does not advise on hazards, exposure limits, waste disposal, containment or emergency procedure. Reagents named in worked examples appear only as arithmetic, and several of them are hazardous.

Before any practical work, follow the safety data sheet for each substance and the rules of the laboratory you are working in, under appropriate supervision.

Acceptable use

You may use the site freely, including for coursework and teaching. You may not:

• Attempt to disrupt the site or the infrastructure serving it.
• Scrape it at a rate that degrades access for other people.
• Present it as your own service, or imply an endorsement that does not exist.

Content and reuse

The text, calculator code, layout and diagrams on this site are the work of its authors. Quoting a short passage or a result with a link back is welcome, and no permission is needed to use a number you calculated here in your own report.

Republishing pages wholesale, or copying the calculators to run elsewhere, is not permitted without written permission. Underlying chemistry is not claimed as anyone's property: the relationships are standard and the sources are listed on the about page.

Changes and contact

These terms may change, and the date at the top of the page changes with them. Questions can go to contact@percentyieldcalculator.org.