About

Gem Carat Calculator is a free set of gemstone weight and size calculators, size charts and guides. Its goal is simple: give shoppers, hobbyists and sellers honest estimates, with the maths shown, instead of a single number that only looks precise.

Who runs the site

Osama Niazi, founder and editor.

Osama has sold handmade rings set with precious, semi-precious and lab-created gemstones on Etsy, eBay and Amazon since 2018. Describing stone size and weight accurately for buyers is part of his daily work, and this site turns that habit into free tools.

The site is independent. It is not affiliated with, endorsed by or connected to the GIA, the International Gem Society, any gem laboratory, retailer or supplier. Those organisations are cited as sources only. The site does not claim any gemological credential or laboratory accreditation.

How the tools are built

Formulas and physical constants come from published gemological and trade references, listed with their sources on the How we calculate page.
Every value is stored in one data file with its source and a cross-checked or approximate status.
All charts and every number quoted in page text are generated from the same engine the calculators use, and automated tests check that they agree.
Results are always shown as a range. We say plainly when a value is approximate.

What the site is not

It is not an appraisal service, a grading laboratory or a price guide. Results are estimates. For value, insurance or identification, consult a qualified, independent professional. See the disclaimer.

How the site is funded

The site may show advertising. Ads never change our numbers or what we write. There are no affiliate links at launch, and if any are ever added they will be clearly disclosed on the page where they appear.

Get in touch

Corrections and suggestions are welcome through the contact page.