How much does a 1.00 to 1.49ct I SI1 lab grown cushion diamond cost?

As of October 2026, 1.00 to 1.49ct I SI1 lab grown cushion diamonds typically cost £255 GBP to £2,651 GBP, with a median price of £698 GBP. There are currently 3 diamonds matching this specification available across retailers.

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

About 31% of these diamonds are available at multiple retailers, with an average price spread of 131%. A comparison tool like Carat Hunter lets you see all the prices side by side.

1.00 to 1.49ct I SI1 Lab Grown Cushion

Quick answer

As of October 2026, there are 3 lab grown cushion diamonds with I colour and SI1 clarity in the 1.00 to 1.49ct range available across retailers worldwide. Prices typically run £255 GBP to £2,651 GBP, with a median of £698 GBP. At least 19 retailers stock this exact specification, and 31% of the stones appear at more than one of them, with an average price spread of 131%. Half of all listings fall between £262 GBP and £783 GBP per carat. The same specification in natural form lists at a median of about £1,815 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. 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: October 2026

Available

Lowest Price

£200 GBP

Highest Price

£3,592 GBP

Average Price

£1,213 GBP

Market Intelligence

Retailers Selling

Cross Retailer %

31.3%

Price Spread

131.4%

Price Range

Price per carat distribution across retailers

$528/ct

10th Percentile

$264

Median

$528

90th Percentile

$2,917

Score Distribution

5 diamonds scored across 3 quality tiers

Excellent

1 (20.0%)

Good

1 (20.0%)

Average

3 (60.0%)

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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