Free tools

Numbers and tells, no jeweller required

Three calculators we built for ourselves and opened up to you. They’re fast, free and honest about their limits — for an insurance-ready answer, our lab takes it from here.

Estimate weight

Carat Weight Calculator

Enter your stone’s length, width and depth in millimetres and pick a shape. We apply the industry-standard formula to estimate carat weight in real time — handy when a stone is set and can’t be weighed loose.

Calculate carat

Ballpark value

Diamond Price Estimator

Dial in carat, cut, colour and clarity to see an indicative price range. Built on real market relationships — price climbs faster than weight, and every grade nudges the band up or down.

Estimate price

Test yourself

Real-vs-Fake Quiz

Six quick questions on the tests that actually separate diamond from moissanite, CZ and glass. Get instant feedback on each, then a verdict on how sharp your eye really is.

Take the quiz

Estimates are a great start. Certainty needs a lab.

These tools can’t tell natural from lab-grown, or diamond from moissanite. When the answer has to be right, send it to us — free photo screening or a numbered certificate.

Verify my diamond Talk to a gemologist