How much does a 3.00 to 4.99ct I SI2 natural cushion diamond cost?

As of October 2026, 3.00 to 4.99ct I SI2 natural cushion diamonds typically cost £13,670 GBP to £43,383 GBP, with a median price of £22,174 GBP. There are currently 112 diamonds matching this specification available across retailers.

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

About 43% of these diamonds are available at multiple retailers, with an average price spread of 36%. A comparison tool like Carat Hunter lets you see all the prices side by side.

3.00 to 4.99ct I SI2 Natural Cushion

Quick answer

As of October 2026, there are 112 natural cushion diamonds with I colour and SI2 clarity in the 3.00 to 4.99ct range available across retailers worldwide. Prices typically run £13,670 GBP to £43,383 GBP, with a median of £22,174 GBP. At least 51 retailers stock this exact specification, and 43% of the stones appear at more than one of them, with an average price spread of 36%. Half of all listings fall between £5,586 GBP and £8,003 GBP per carat. The same specification in lab grown form lists at a median of about £503 GBP per carat. Over the last 30 days the median price moved -0.7% and the number of listings moved +12.9%.

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. Cushion natural stones in the index: 2,948 USD per carat, +1.7% 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

112

Lowest Price

£8,143 GBP

Highest Price

£92,108 GBP

Average Price

£25,930 GBP