Scope.
This index tracks listed retail prices (not transaction prices) across major UK online lab-grown diamond retailers. The October 2026 edition collected 2,360 round G VS1 IGI lab-grown diamond listings (before each retailer's own Excellent-cut filter) across three retailers. All prices are in GBP, inclusive of 20% UK VAT (inc-VAT). Data was collected on October 25, 2026. This is the sixth edition; the retailer panel is unchanged since the May 2026 inaugural edition.
Coverage this edition.
Quality Diamonds' listed inventory rebounded between the September and October collections: 380 listings collected this edition (81 at 1ct, 154 at 1.5ct, 145 at 2ct) against 74 in September and 402 in August. A same-day re-query of the retailer's own inventory API on 2026-10-25 returned identical counts, confirming a genuine change in listed stock rather than a collection issue. Counted Excellent-cut and IGI only (the Excellent-cut filter has applied to Quality Diamonds since the 2026-09-18 correction; this edition also restricts the count to IGI-certified stones, which removes one GIA-certified stone at 1.5ct and does not change that cell's median), Quality Diamonds has n=20 at 1ct, n=83 at 1.5ct and n=51 at 2ct. The 30-listing minimum is unchanged, so 1.5ct and 2ct are published and 1ct is not. Diamond Labs and 77 Diamonds both cleared the minimum at every weight; Diamond Labs' 1ct cell (n=33) is only just above it, and its collected stock fell from 870 listings in September to 666. All three collections were made October 25, 2026, and no feed outage was observed. September's published figures are not restated: every edition is a frozen snapshot once published.
Month-over-month.
Per carat, ex-VAT, September to October: Diamond Labs 0% at 1ct (£207 to £206), +1% at 1.5ct (£172 to £174), -1% at 2ct (£172 to £170); 77 Diamonds -2% at 1ct (£251 to £246), -4% at 1.5ct (£241 to £232), +1% at 2ct (£234 to £236); Quality Diamonds was unpublished in September, so it has no month-over-month comparison at any weight. Published Market Medians: 1ct £271, -1% from September's £275, on the same two retailers; 1.5ct £391, +5% from September's £371, but now on three retailers where September's drew on two; 2ct £478, -2% from September's £487, also now on three retailers. On September's two-retailer panel (Diamond Labs, 77 Diamonds) the October Market Medians would be £271 at 1ct, £365 at 1.5ct (-2%) and £487 at 2ct (0%). The 1.5ct and 2ct changes in the published Market Medians therefore mostly reflect the larger panel, not a market move.
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 October 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 in the Excluded retailers note 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. Published figures in the index table include 20% UK VAT applied to the collected ex-VAT price. Ex-VAT medians (per carat) for October 2026: Diamond Labs 1ct £206 (n=33), 1.5ct £174 (n=112), 2ct £170 (n=89). 77 Diamonds 1ct £246 (n=192), 1.5ct £232 (n=730), 2ct £236 (n=392). Quality Diamonds 1.5ct £217 (n=83) and 2ct £199 (n=51); at 1ct it is below the publication minimum (n=20; see Coverage this edition). The following are excluded: promotional codes, membership discounts, negotiated pricing, and strikethrough compare-at or was-£X 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 the 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 per retailer is required for that retailer's cell to be published, and a Market Median requires at least two qualifying retailers in that cell; a single retailer's price is shown individually but is not published as a market figure. Per-cell sample sizes (n) are visible as tooltips when hovering over any price in the table. Quality Diamonds is below the retailer threshold at 1ct this edition (n=20) and meets it at 1.5ct (n=83) and 2ct (n=51), counted Excellent-cut and IGI only (see Coverage this edition); Diamond Labs and 77 Diamonds met the threshold at every weight.
Deduplication.
Listings are deduplicated within each retailer by URL. Stones with identical IGI certificate numbers may appear at more than one retailer and are counted as independent listings at each retailer where they appear.
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.
Comparability.
The UK and US indices are not directly comparable: the UK index uses G VS1 and reports in GBP inc-VAT; the US index uses E VS1 and reports in USD. Historical index figures may not be directly comparable when the benchmark specification, the retailer panel, or the set of retailers with published cells changes; this edition's 1ct Market Median draws on two retailers (Diamond Labs, 77 Diamonds) and its 1.5ct and 2ct Market Medians draw on three, where September's drew on two, after Quality Diamonds' listed inventory recovered above the publication minimum at those two weights (see Coverage this edition).
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.