How much does a 5.00ct+ I SI1 natural cushion diamond cost?

As of November 2026, 5.00ct+ I SI1 natural cushion diamonds typically cost HK$436,134 HKD to HK$1,422,136 HKD, with a median price of HK$667,878 HKD. There are currently 19 diamonds matching this specification available across retailers.

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

About 26% of these diamonds are available at multiple retailers, with an average price spread of 36%. A comparison tool like Carat Hunter lets you see all the prices side by side.

5.00ct+ I SI1 Natural Cushion

Quick answer

As of November 2026, there are 19 natural cushion diamonds with I colour and SI1 clarity in the 5.00ct+ range available across retailers worldwide. Prices typically run HK$436,134 HKD to HK$1,422,136 HKD, with a median of HK$667,878 HKD. At least 46 retailers stock this exact specification, and 26% of the stones appear at more than one of them, with an average price spread of 36%. Half of all listings fall between HK$111,408 HKD and HK$161,797 HKD per carat. The same specification in lab grown form lists at a median of about HK$25,826 HKD per carat. Over the last 30 days the median price moved -1.5% and the number of listings moved -2.6%.

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 natural stones in the index: 2,948 USD per carat, +1.7% 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: November 2026

Available

Lowest Price

HK$328,499 HKD

Highest Price

HK$2,872,898 HKD

Average Price

HK$826,354 HKD

Market Intelligence

Retailers Selling

Cross Retailer %

26.2%

Price Spread

35.9%

30-Day Price Trend

-1.5%

30-Day Supply Change

-2.6%

Volatility (30d)

0.01

Price Range

Price per carat distribution across retailers

$17,899/ct

10th Percentile

$11,381

Median

$17,899

90th Percentile

$23,030

Score Distribution

42 diamonds scored across 4 quality tiers

Excellent

6 (14.3%)

Very Good

6 (14.3%)

Good

10 (23.8%)

Average

20 (47.6%)

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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