How much does a 0.20 to 0.49ct I SI1 lab grown round diamond cost?

As of October 2026, 0.20 to 0.49ct I SI1 lab grown round diamonds typically cost £101 GBP to £578 GBP, with a median price of £286 GBP. There are currently 29 diamonds matching this specification available across retailers.

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

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0.20 to 0.49ct I SI1 Lab Grown Round

Quick answer

As of October 2026, there are 29 lab grown round diamonds with I colour and SI1 clarity in the 0.20 to 0.49ct range available across retailers worldwide. Prices typically run £101 GBP to £578 GBP, with a median of £286 GBP. The same specification in natural form lists at a median of about £1,029 GBP per carat.

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

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. Round lab grown stones in the index: 414 USD per carat, -5.0% 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: October 2026

Available

Lowest Price

£96 GBP

Highest Price

£754 GBP

Average Price

£326 GBP

Score Distribution

73 diamonds scored across 4 quality tiers

Excellent

1 (1.4%)

Very Good

17 (23.3%)

Good

38 (52.1%)

Average

17 (23.3%)

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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