Diamond buying guide

Cut

Cut is the quality of a diamond's proportions, symmetry and polish, and it has the biggest effect on sparkle. For round brilliants, choose Excellent (GIA) or Ideal (IGI). Fancy shapes have no official cut grade, so we assess depth, table and light performance for you. Antique cuts are judged by character rather than by modern grades.

Colour

White diamonds are graded D (colourless) to Z (light yellow). D–F are colourless, G–J near-colourless. Set in yellow or rose gold, H–J can look just as white as higher grades and save significant budget. Fancy colours use a separate scale of hue and intensity.

Clarity

Clarity grades inclusions from Flawless (FL) to Included (I1–I3). Most people cannot see inclusions without magnification from VS2 upward in brilliant cuts. Step cuts such as emerald and Asscher show more, so we suggest VS1 or better there.

Carat

Carat is weight: one carat equals 0.2 grams. Prices jump at "magic" weights such as 0.50, 1.00 and 1.50 ct, so a 0.95 ct stone can look identical to a 1.00 ct and cost less. Elongated shapes like oval, pear and marquise face up larger than a round of the same weight.

Certificate

Always buy a diamond with an independent grading report. GIA is the most widely recognised for natural diamonds; IGI is the leading laboratory for lab-grown. Read more on our certification page.

Fluorescence

Some diamonds glow blue under UV light. Faint to medium fluorescence rarely affects appearance and can reduce price. Very strong fluorescence can occasionally cause a hazy look, which we check on video.