How much does a 1.50 to 1.99ct I SI1 lab grown cushion diamond cost?

As of October 2026, 1.50 to 1.99ct I SI1 lab grown cushion diamonds typically cost £275 GBP to £1,867 GBP, with a median price of £1,114 GBP. There are currently 23 diamonds matching this specification available across retailers.

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

About 37% of these diamonds are available at multiple retailers, with an average price spread of 113%. A comparison tool like Carat Hunter lets you see all the prices side by side.

1.50 to 1.99ct I SI1 Lab Grown Cushion

Quick answer

As of October 2026, there are 23 lab grown cushion diamonds with I colour and SI1 clarity in the 1.50 to 1.99ct range available across retailers worldwide. Prices typically run £275 GBP to £1,867 GBP, with a median of £1,114 GBP. At least 28 retailers stock this exact specification, and 37% of the stones appear at more than one of them, with an average price spread of 113%. Half of all listings fall between £266 GBP and £792 GBP per carat. The same specification in natural form lists at a median of about £2,799 GBP per carat. Over the last 30 days the median price moved -4.9% and the number of listings moved +0.3%.

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

£193 GBP

Highest Price

£5,817 GBP

Average Price

£1,207 GBP

Market Intelligence

Retailers Selling

Cross Retailer %

36.5%

Price Spread

113.0%

30-Day Price Trend

-4.9%

30-Day Supply Change

+0.3%

Volatility (30d)

0.03

Price Range

Price per carat distribution across retailers

$619/ct

10th Percentile

$278

Median

$619

90th Percentile

$1,586

Score Distribution

39 diamonds scored across 4 quality tiers

Excellent

4 (10.3%)

Very Good

12 (30.8%)

Good

11 (28.2%)

Average

12 (30.8%)

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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