How much does a 1.00 to 1.49ct I SI1 natural radiant diamond cost?

As of October 2026, 1.00 to 1.49ct I SI1 natural radiant diamonds typically cost £1,152 GBP to £3,594 GBP, with a median price of £1,952 GBP. There are currently 254 diamonds matching this specification available across retailers.

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

About 35% of these diamonds are available at multiple retailers, with an average price spread of 56%. A comparison tool like Carat Hunter lets you see all the prices side by side.

1.00 to 1.49ct I SI1 Natural Radiant

Quick answer

As of October 2026, there are 254 natural radiant diamonds with I colour and SI1 clarity in the 1.00 to 1.49ct range available across retailers worldwide. Prices typically run £1,152 GBP to £3,594 GBP, with a median of £1,952 GBP. At least 65 retailers stock this exact specification, and 35% of the stones appear at more than one of them, with an average price spread of 56%. Half of all listings fall between £1,439 GBP and £2,450 GBP per carat. The same specification in lab grown form lists at a median of about £579 GBP per carat. Over the last 30 days the median price moved -0.6% and the number of listings moved +16.3%.

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

254

Lowest Price

£694 GBP

Highest Price

£6,423 GBP

Average Price

£2,148 GBP