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

As of September 2026, 1.00 to 1.49ct I SI1 natural cushion diamonds typically cost £903 GBP to £2,775 GBP, with a median price of £1,583 GBP. There are currently 1,119 diamonds matching this specification available across retailers.

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

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1.00 to 1.49ct I SI1 Natural Cushion

Quick answer

As of September 2026, there are 1,119 natural cushion diamonds with I colour and SI1 clarity in the 1.00 to 1.49ct range available across retailers worldwide. Prices typically run £903 GBP to £2,775 GBP, with a median of £1,583 GBP. At least 56 retailers stock this exact specification. Half of all listings fall between £1,227 GBP and £2,151 GBP per carat. The same specification in lab grown form lists at a median of about £1,035 GBP per carat.

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

Caratlytics Diamond Price Index, August 2026: natural diamonds at 2,184 USD per carat and lab-grown at 464 USD per carat, a natural to lab ratio of 4.7 to 1. Cushion natural stones in the index: 2,792 USD per carat, +1.1% month on month. See the full index release

Figures come from live listings across more than 100 retailers and refresh daily. The index is a monthly release.

Last updated: September 2026

Available

1,119

Lowest Price

£600 GBP

Highest Price

£6,846 GBP

Average Price

£1,759 GBP

Market Intelligence

Retailers Selling

Price Spread

57.6%

Price Range

Price per carat distribution across retailers

$2,160/ct

10th Percentile

$1,369

Median

$2,160

90th Percentile

$3,768

Score Distribution

1.1K diamonds scored across 4 quality tiers

Excellent

171 (15.3%)

Very Good

280 (25.0%)

Good

412 (36.8%)

Average

256 (22.9%)

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Consider Instead

Save money without compromising on what matters. These alternatives are visually similar but cost less.

J SI1J colour is visually identical to I to the naked eye

Save 25%

Lab-Grown I SI1Same specifications, lab-grown origin

Save 38%

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