How much does a 0.75 to 0.99ct I SI1 natural radiant diamond cost?

As of October 2026, 0.75 to 0.99ct I SI1 natural radiant diamonds typically cost £779 GBP to £2,047 GBP, with a median price of £1,157 GBP. There are currently 58 diamonds matching this specification available across retailers.

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

About 26% of these diamonds are available at multiple retailers, with an average price spread of 54%. A comparison tool like Carat Hunter lets you see all the prices side by side.

0.75 to 0.99ct I SI1 Natural Radiant

Quick answer

As of October 2026, there are 58 natural radiant diamonds with I colour and SI1 clarity in the 0.75 to 0.99ct range available across retailers worldwide. Prices typically run £779 GBP to £2,047 GBP, with a median of £1,157 GBP. At least 55 retailers stock this exact specification, and 26% of the stones appear at more than one of them, with an average price spread of 54%. Half of all listings fall between £1,177 GBP and £1,987 GBP per carat. The same specification in lab grown form lists at a median of about £534 GBP per carat. Over the last 30 days the median price moved +1.2% and the number of listings moved +8.7%.

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. Radiant natural stones in the index: 3,091 USD per carat, +13.2% 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

£416 GBP

Highest Price

£3,736 GBP

Average Price

£1,282 GBP