How much does a 1.50 to 1.99ct I SI1 natural radiant diamond cost?

As of October 2026, 1.50 to 1.99ct I SI1 natural radiant diamonds typically cost £3,023 GBP to £7,492 GBP, with a median price of £4,971 GBP. There are currently 189 diamonds matching this specification available across retailers.

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

About 36% 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.

1.50 to 1.99ct I SI1 Natural Radiant

Quick answer

As of October 2026, there are 189 natural radiant diamonds with I colour and SI1 clarity in the 1.50 to 1.99ct range available across retailers worldwide. Prices typically run £3,023 GBP to £7,492 GBP, with a median of £4,971 GBP. At least 62 retailers stock this exact specification, and 36% of the stones appear at more than one of them, with an average price spread of 46%. Half of all listings fall between £2,699 GBP and £4,245 GBP per carat. The same specification in lab grown form lists at a median of about £795 GBP per carat. Over the last 30 days the median price moved -0.8% and the number of listings moved +16.4%.

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

189

Lowest Price

£1,729 GBP

Highest Price

£15,000 GBP

Average Price

£5,247 GBP