How much does a 5.00ct+ I SI2 lab grown cushion diamond cost?

As of September 2026, 5.00ct+ I SI2 lab grown cushion diamonds typically cost £60,426 GBP to £69,921 GBP, with a median price of £67,472 GBP. There are currently 3 diamonds matching this specification available across retailers.

Where can I find the best price on a I SI2 cushion diamond?

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5.00ct+ I SI2 Lab Grown Cushion

Quick answer

As of September 2026, there are 3 lab grown cushion diamonds with I colour and SI2 clarity in the 5.00ct+ range available across retailers worldwide. Prices typically run £60,426 GBP to £69,921 GBP, with a median of £67,472 GBP. At least 7 retailers stock this exact specification. Half of all listings fall between £736 GBP and £10,389 GBP per carat. The same specification in natural form lists at a median of about £14,340 GBP per carat.

Caratlytics Diamond Price Index, August 2026: natural diamonds at 2,184 USD per carat and lab-grown at 464 USD per carat, a natural to lab ratio of 4.7 to 1. Cushion lab grown stones in the index: 466 USD per carat, -14.7% month on month. See the full index release

Figures come from live listings across more than 100 retailers and refresh daily. The index is a monthly release.

Last updated: September 2026

Available

Lowest Price

£58,665 GBP

Highest Price

£70,533 GBP

Average Price

£65,557 GBP

Market Intelligence

Retailers Selling

Price Spread

474.8%

Price Range

Price per carat distribution across retailers

$2,746/ct

10th Percentile

$274

Median

$2,746

90th Percentile

$16,087

Score Distribution

3 diamonds scored across 1 quality tiers

Average

3 (100.0%)

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Related Specifications

D IF D VVS1 D VVS2 D VS1 D VS2 D SI1 E IF E VVS1 E VVS2 E VS1 E VS2 E SI1 F IF F VVS1 F VVS2 F VS1 F VS2 F SI1 G IF G VVS1 G VVS2 G VS1 G VS2 G SI1 H IF H VVS1 H VVS2 H VS1 H VS2 H SI1 I IF I VVS1 I VVS2 I VS1 I VS2 I SI1