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 $79,817 AUD to $260,396 AUD, with a median price of $128,626 AUD. There are currently 63 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 63 natural cushion diamonds with I colour and SI1 clarity in the 5.00ct+ range available across retailers worldwide. Prices typically run $79,817 AUD to $260,396 AUD, with a median of $128,626 AUD. At least 37 retailers stock this exact specification. Half of all listings fall between $20,325 AUD and $30,402 AUD per carat. The same specification in lab grown form lists at a median of about $1,675 AUD 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

$54,897 AUD

Highest Price

$552,980 AUD

Average Price

$150,285 AUD

Market Intelligence

Retailers Selling

Price Spread

38.9%

Price Range

Price per carat distribution across retailers

$16,830/ct

10th Percentile

$9,325

Median

$16,830

90th Percentile

$21,594

Score Distribution

63 diamonds scored across 4 quality tiers

Excellent

5 (7.9%)

Very Good

16 (25.4%)

Good

23 (36.5%)

Average

19 (30.2%)

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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