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

As of October 2026, 5.00ct+ I SI1 natural round diamonds typically cost $107,031 AUD to $260,356 AUD, with a median price of $148,055 AUD. There are currently 91 diamonds matching this specification available across retailers.

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

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5.00ct+ I SI1 Natural Round

Quick answer

As of October 2026, there are 91 natural round diamonds with I colour and SI1 clarity in the 5.00ct+ range available across retailers worldwide. Prices typically run $107,031 AUD to $260,356 AUD, with a median of $148,055 AUD. The same specification in lab grown form lists at a median of about $513 AUD 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. Round natural stones in the index: 2,248 USD per carat, +7.6% 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

$53,721 AUD

Highest Price

$736,443 AUD

Average Price

$169,697 AUD

Score Distribution

249 diamonds scored across 4 quality tiers

Excellent

29 (11.6%)

Very Good

55 (22.1%)

Good

64 (25.7%)

Average

101 (40.6%)

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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