Lab grown diamond prices, from a real price book.

Diamonds are priced per carat within a size band, and larger bands carry a higher rate. A 2 carat stone therefore costs more than two 1 carat stones of the same grade — bigger rough is rarer, even when it is grown.

The bands start at the size quoted. A 1.20 ct stone is priced at the 1 ct band rate until the next quoted size, which is why the estimator asks for the exact carat rather than a rounded one.

OUVRA works in three clarities — VVS1, VVS2 and VS1 — with no inclusions visible to the naked eye at normal viewing distance in a well-cut stone. Moving up a clarity grade adds to the rate; the table shows how much at each size.

Colourless stones are quoted in E and F. Fancy colours — yellow, blue, pink and brown — are priced on their own scale from 1 carat upwards, and their final figure moves a little with the shape.

Each shape is priced on its own sheet. Round, oval, emerald, pear, cushion, princess, radiant and marquise each have their own rates, and the difference between them changes with size — compare round and oval in the table.

A finished ring adds gold, charged by weight at the day's rate, the making of the piece and an independent certificate. The worked example below is the same ring the OUVRA homepage prices, line by line.

Every figure is indicative. Gold moves daily and the final metal weight is confirmed when you approve the CAD, so the quotation can move a little either way.