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

As of September 2026, 5.00ct+ I SI1 natural round diamonds typically cost £41,338 GBP to £123,910 GBP, with a median price of £69,055 GBP. There are currently 311 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 September 2026, there are 311 natural round diamonds with I colour and SI1 clarity in the 5.00ct+ range available across retailers worldwide. Prices typically run £41,338 GBP to £123,910 GBP, with a median of £69,055 GBP. At least 5 retailers stock this exact specification. Half of all listings fall between £9,143 GBP and £14,154 GBP per carat. The same specification in lab grown form lists at a median of about £828 GBP 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. Round natural stones in the index: 2,094 USD per carat, -3.8% 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

311

Lowest Price

£18,809 GBP

Highest Price

£386,391 GBP

Average Price

£81,125 GBP

Market Intelligence

Retailers Selling

Price Spread

40.1%

Price Range

Price per carat distribution across retailers

$16,887/ct

10th Percentile

$11,259

Median

$16,887

90th Percentile

$20,569

Score Distribution

311 diamonds scored across 4 quality tiers

Excellent

52 (16.7%)

Very Good

78 (25.1%)

Good

106 (34.1%)

Average

75 (24.1%)

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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