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

As of September 2026, 5.00ct+ I SI1 natural cushion diamonds typically cost HK$412,356 HKD to HK$1,303,822 HKD, with a median price of HK$655,889 HKD. There are currently 65 diamonds matching this specification available across retailers.

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

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5.00ct+ I SI1 Natural Cushion

Quick answer

As of September 2026, there are 65 natural cushion diamonds with I colour and SI1 clarity in the 5.00ct+ range available across retailers worldwide. Prices typically run HK$412,356 HKD to HK$1,303,822 HKD, with a median of HK$655,889 HKD. At least 37 retailers stock this exact specification. Half of all listings fall between HK$106,598 HKD and HK$156,618 HKD per carat. The same specification in lab grown form lists at a median of about HK$10,855 HKD 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. Cushion natural stones in the index: 2,792 USD per carat, +1.1% 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

Lowest Price

HK$279,930 HKD

Highest Price

HK$2,819,748 HKD

Average Price

HK$762,590 HKD

Market Intelligence

Retailers Selling

Price Spread

37.8%

Price Range

Price per carat distribution across retailers

$16,874/ct

10th Percentile

$9,863

Median

$16,874

90th Percentile

$21,839

Score Distribution

65 diamonds scored across 4 quality tiers

Excellent

5 (7.7%)

Very Good

17 (26.2%)

Good

24 (36.9%)

Average

19 (29.2%)

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Consider Instead

Save money without compromising on what matters. These alternatives are visually similar but cost less.

Lab-Grown I SI1Same specifications, lab-grown origin

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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