How much does a 5.00ct+ J SI1 lab grown cushion diamond cost?

As of November 2026, 5.00ct+ J SI1 lab grown cushion diamonds typically cost £4,481 GBP to £26,495 GBP, with a median price of £15,488 GBP. There are currently 1 diamonds matching this specification available across retailers.

Where can I find the best price on a J SI1 cushion diamond?

About 50% of these diamonds are available at multiple retailers, with an average price spread of 149%. A comparison tool like Carat Hunter lets you see all the prices side by side.

5.00ct+ J SI1 Lab Grown Cushion

Quick answer

As of November 2026, there are 1 lab grown cushion diamonds with J colour and SI1 clarity in the 5.00ct+ range available across retailers worldwide. Prices typically run £4,481 GBP to £26,495 GBP, with a median of £15,488 GBP. At least 11 retailers stock this exact specification, and 50% of the stones appear at more than one of them, with an average price spread of 149%. Half of all listings fall between £378 GBP and £1,074 GBP per carat. The same specification in natural form lists at a median of about £9,033 GBP per carat.

Three of the best scored stones at this specification right now:

5.02ct Cushion J SI1, IGI, grade B+, from £1,729 GBP

Caratlytics Diamond Price Index, September 2026: natural diamonds at 2,335 USD per carat and lab-grown at 443 USD per carat, a natural to lab ratio of 5.3 to 1. Cushion lab grown stones in the index: 516 USD per carat, +6.9% month on month. See the full index release

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

Last updated: November 2026

Available

Lowest Price

£1,729 GBP

Highest Price

£43,813 GBP

Average Price

£15,488 GBP

Market Intelligence

Retailers Selling

Cross Retailer %

50.0%

Price Spread

149.1%

Price Range

Price per carat distribution across retailers

$625/ct

10th Percentile

$479

Median

$625

90th Percentile

$7,822

Score Distribution

2 diamonds scored across 1 quality tiers

Very Good

2 (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