How much does a 5.00ct+ I SI2 natural round diamond cost?

As of October 2026, 5.00ct+ I SI2 natural round diamonds typically cost £31,476 GBP to £104,509 GBP, with a median price of £59,230 GBP. There are currently 116 diamonds matching this specification available across retailers.

Where can I find the best price on a I SI2 round diamond?

About 44% of these diamonds are available at multiple retailers, with an average price spread of 30%. A comparison tool like Carat Hunter lets you see all the prices side by side.

5.00ct+ I SI2 Natural Round

Quick answer

As of October 2026, there are 116 natural round diamonds with I colour and SI2 clarity in the 5.00ct+ range available across retailers worldwide. Prices typically run £31,476 GBP to £104,509 GBP, with a median of £59,230 GBP. At least 10 retailers stock this exact specification, and 44% of the stones appear at more than one of them, with an average price spread of 30%. Half of all listings fall between £8,831 GBP and £12,139 GBP per carat. Over the last 30 days the median price moved +4.3% and the number of listings moved +0.8%.

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

116

Lowest Price

£22,047 GBP

Highest Price

£687,672 GBP

Average Price

£69,647 GBP

Market Intelligence

Retailers Selling

Cross Retailer %

44.4%

Price Spread

30.2%

30-Day Price Trend

+4.3%

30-Day Supply Change

+0.8%

Volatility (30d)

0.01

Price Range

Price per carat distribution across retailers

$14,589/ct

10th Percentile

$10,454

Median

$14,589

90th Percentile

$17,714

Score Distribution

308 diamonds scored across 4 quality tiers

Excellent

76 (24.7%)

Very Good

47 (15.3%)

Good

69 (22.4%)

Average

116 (37.7%)

Find Your Diamond

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Consider Instead

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

J SI2J colour is visually identical to I to the naked eye

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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