How much does a 3.00 to 4.99ct I SI1 lab grown radiant diamond cost?

As of September 2026, 3.00 to 4.99ct I SI1 lab grown radiant diamonds typically cost £2,947 GBP to £30,657 GBP, with a median price of £4,658 GBP. There are currently 102 diamonds matching this specification available across retailers.

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

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3.00 to 4.99ct I SI1 Lab Grown Radiant

Quick answer

As of September 2026, there are 102 lab grown radiant diamonds with I colour and SI1 clarity in the 3.00 to 4.99ct range available across retailers worldwide. Prices typically run £2,947 GBP to £30,657 GBP, with a median of £4,658 GBP. At least 24 retailers stock this exact specification. Half of all listings fall between £427 GBP and £1,391 GBP per carat. The same specification in natural form lists at a median of about £9,783 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. Radiant lab grown stones in the index: 473 USD per carat, -12.5% 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

102

Lowest Price

£384 GBP

Highest Price

£57,906 GBP

Average Price

£8,849 GBP

Market Intelligence

Retailers Selling

Price Spread

74.6%

Price Range

Price per carat distribution across retailers

$1,747/ct

10th Percentile

$276

Median

$1,747

90th Percentile

$3,228

Score Distribution

102 diamonds scored across 4 quality tiers

Excellent

3 (2.9%)

Very Good

9 (8.8%)

Good

75 (73.5%)

Average

15 (14.7%)

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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