How much does a 3.00 to 4.99ct I SI2 lab grown round diamond cost?

As of September 2026, 3.00 to 4.99ct I SI2 lab grown round diamonds typically cost £3,482 GBP to £45,204 GBP, with a median price of £26,099 GBP. There are currently 56 diamonds matching this specification available across retailers.

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

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3.00 to 4.99ct I SI2 Lab Grown Round

Quick answer

As of September 2026, there are 56 lab grown round diamonds with I colour and SI2 clarity in the 3.00 to 4.99ct range available across retailers worldwide. Prices typically run £3,482 GBP to £45,204 GBP, with a median of £26,099 GBP. At least 25 retailers stock this exact specification. Half of all listings fall between £3,940 GBP and £9,137 GBP per carat. The same specification in natural form lists at a median of about £7,559 GBP per carat.

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

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. Round lab grown stones in the index: 438 USD per carat, -14.1% 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

£296 GBP

Highest Price

£76,721 GBP

Average Price

£25,198 GBP

Market Intelligence

Retailers Selling

Price Spread

80.9%

Price Range

Price per carat distribution across retailers

$8,681/ct

10th Percentile

$1,384

Median

$8,681

90th Percentile

$15,065

Score Distribution

56 diamonds scored across 4 quality tiers

Excellent

2 (3.6%)

Very Good

20 (35.7%)

Good

7 (12.5%)

Average

27 (48.2%)

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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