UK Lab-Grown Diamond Price Index

Three retailers. 2,550 listings. G VS1 Round Excellent IGI.

• Prices fell sharply since the May inaugural edition, concentrated at larger weights. The 2ct market median dropped from £1,051 to £482 (down 54%) and 1.5ct from £661 to £400 (down 39%), while 1ct held roughly flat (£305 to £304).
• The size premium has compressed. A 2ct G VS1 round now costs less per carat than a 1ct at every retailer in the panel: the usual reward for buying larger has nearly vanished at the lab-grown benchmark grade.
• The price difference is not a quality difference. It is a retailer difference. At 2ct, the gap reaches £175 on a single stone.
• Diamond Labs ranked cheapest at all three weight tiers.
• What UK buyers assume is a cross-border premium is VAT and exchange rate, not markup. Brilliant Earth UK is excluded from this index: their GBP prices are derived from a USD conversion formula, not independently set for the UK market.
• We audited six UK retailers. Three qualified. London-based Queensmith passed structural eligibility but carries zero G-color lab-grown diamonds. Their inventory is exclusively D, E, and F color, confirmed via live API across all carat bands. A three-retailer result at G VS1 is not a methodology gap. It is the market.
• All prices inc-VAT (20% UK VAT included). Ex-VAT figures are in the methodology section.
• The UK index tracks G VS1, the highest-volume lab-grown specification across UK retailers. The Rings.com US index uses E VS1. Not directly comparable. E commands a color premium over G.

Scope. This index tracks listed retail prices (not transaction prices) across major UK online lab-grown diamond retailers. The June 2026 edition covers 2,550 benchmark-matching lab-grown diamond listings across three retailers. All prices are in GBP, inclusive of 20% UK VAT (inc-VAT). Data was collected in June 2026. This is the second edition; the May 2026 inaugural edition covered 2,706 listings, and the retailer panel is unchanged.

Month-over-month. Between the May and June editions, the market median fell 54% at 2ct (£1,051 to £482) and 39% at 1.5ct (£661 to £400), while the 1ct median was essentially flat (£305 to £304). The decline is concentrated at the larger weights and has compressed the per-carat size premium: a 2ct now prices below a 1ct on a per-carat basis at all three retailers. This mirrors a broader lab-grown wholesale price decline observed in the same period in the Rings.com US index.

Retailer panel. This edition tracks three retailers: Diamond Labs, 77 Diamonds, and Quality Diamonds. The panel was established in May 2026, when eight retailers were evaluated and three qualified, and it is unchanged for June 2026. Two retailers (Brilliant Earth UK and James Allen) were screened out before formal audit: both price in GBP via USD conversion rather than independently setting UK prices. Six retailers proceeded to formal audit against four criteria: (1) live filterable inventory API with no credentials required, (2) publicly visible per-listing GBP pricing, (3) IGI certification as a filterable and per-listing attribute, and (4) minimum 30 qualifying listings per carat cell. Three qualified. Three were excluded; exclusion reasons are documented below. The panel is fixed and disclosed for comparability. Any additions, removals, or reclassifications will be explicitly noted in that month's report.

Excluded retailers. Queensmith (queensmith.co.uk) passed structural eligibility criteria but stocks exclusively D, E, and F color lab-grown diamonds: a live API query found zero G-color listings across all three benchmark carat bands, consistent with their premium-positioning sourcing standard. Purely Diamonds (purelydiamonds.co.uk) and Angelic Diamonds (angelicdiamonds.com) are finished jewelry retailers with no loose diamond search inventory.

Price inputs. Prices are the publicly visible list price at the time of data collection, inclusive of 20% UK VAT in the index table. Ex-VAT medians (per carat) for June 2026: Diamond Labs 1ct £203, 1.5ct £171, 2ct £163. 77 Diamonds 1ct £253, 1.5ct £247, 2ct £236. Quality Diamonds 1ct £278, 1.5ct £222, 2ct £201. The following are excluded: promotional codes, membership discounts, negotiated pricing, and strikethrough compare-at reference prices.

Benchmark specification. The benchmark specification is G color, VS1 clarity, round brilliant, Excellent cut, IGI-certified. G color was chosen because it is the highest-volume specification available with consistent depth across all three tracked UK retailers. Three weight cells are tracked: 1ct (0.95-1.05ct), 1.5ct (1.45-1.55ct), and 2ct (1.95-2.05ct). Note: the Rings.com US price index uses E color rather than G color. E is a higher color grade and commands a price premium. Cross-market comparisons between the US and UK indices should account for this grade difference.

Statistical method. Each published figure is the median total stone price across all qualifying listings within that cell. Median is used instead of an average to reduce the influence of extreme outlier listings. A minimum of 30 qualifying listings is required for publication. All cells in this edition meet that threshold.

Data sourcing. The UK index is built from live API queries against each retailer's product inventory backend. All three APIs are public-facing endpoints that power the retailers' own consumer-facing search pages. No credentials, scraper accounts, or private API keys were used.

Market concentration. The UK online lab-grown market is tracked here across three retailers (Diamond Labs, 77 Diamonds, and Quality Diamonds): the primary UK-accessible online retailers with independently-priced GBP inventory and sufficient benchmark-matching stock to produce stable medians across all three carat tiers. A pricing decision by a single UK retailer will move the index median more than an equivalent decision would move the US index.

Independence. Rings.com receives no compensation from the retailers included in this index for inclusion or ranking, and no retailer has any editorial control over the methodology or results. This index reflects public list prices only; individual purchase prices may differ due to custom configurations, time-sensitive promotions, or VAT treatment at purchase.