How much does a 3.00 to 4.99ct K SI1 natural cushion diamond cost?

As of November 7, 2026, 3.00 to 4.99ct K SI1 natural cushion diamonds typically cost £10,151 GBP to £33,295 GBP, with a median price of £17,077 GBP. There are currently 154 diamonds matching this specification available across retailers.

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

About 35% of these diamonds are available at multiple retailers, with an average price spread of 46%. A comparison tool like Carat Hunter lets you see all the prices side by side.

3.00 to 4.99ct K SI1 Natural Cushion

Quick answer

As of November 7, 2026, there are 154 natural cushion diamonds with K colour and SI1 clarity in the 3.00 to 4.99ct range available across retailers worldwide. Prices typically run £10,151 GBP to £33,295 GBP, with a median of £17,077 GBP. Half of all listings fall between £3,949 GBP and £6,331 GBP per carat. The same specification in lab grown form lists at a median of about £1,276 GBP per carat. Over the last 30 days the median price moved -0.9% and the number of listings moved +6.8%.

Three of the best scored stones at this specification right now:

Caratlytics Diamond Price Index, October 2026: natural diamonds at 2,202 USD per carat and lab-grown at 462 USD per carat, a natural to lab ratio of 4.8 to 1. Cushion natural stones in the index: 2,881 USD per carat, -2.5% month on month. See the full index release

Figures come from current listings across more than 125 retailers. The index is a monthly release.

Last updated: November 7, 2026

Available

154

Lowest Price

£4,698 GBP

Highest Price

£53,450 GBP

Average Price

£19,319 GBP

Market Intelligence

Cross Retailer %

35.1%

Price Spread

45.6%

30-Day Price Trend

-0.9%

30-Day Supply Change

+6.8%

Volatility (30d)

0.01

Price Range

Price per carat distribution across retailers

$6,990/ct

10th Percentile

$4,447

Median

$6,990

90th Percentile

$11,251

Score Distribution

154 diamonds scored across 4 quality tiers

Excellent

26 (16.9%)

Very Good

45 (29.2%)

Good

35 (22.7%)

Average

48 (31.2%)

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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