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

As of October 2026, 1.00 to 1.49ct I SI1 natural cushion diamonds typically cost £887 GBP to £2,853 GBP, with a median price of £1,653 GBP. There are currently 560 diamonds matching this specification available across retailers.

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

About 35% of these diamonds are available at multiple retailers, with an average price spread of 60%. A comparison tool like Carat Hunter lets you see all the prices side by side.

1.00 to 1.49ct I SI1 Natural Cushion

Quick answer

As of October 2026, there are 560 natural cushion diamonds with I colour and SI1 clarity in the 1.00 to 1.49ct range available across retailers worldwide. Prices typically run £887 GBP to £2,853 GBP, with a median of £1,653 GBP. At least 63 retailers stock this exact specification, and 35% of the stones appear at more than one of them, with an average price spread of 60%. Half of all listings fall between £1,212 GBP and £2,179 GBP per carat. The same specification in lab grown form lists at a median of about £418 GBP per carat. Over the last 30 days the median price moved -1.6% and the number of listings moved +9.9%.

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

560

Lowest Price

£616 GBP

Highest Price

£6,533 GBP

Average Price

£1,799 GBP

Market Intelligence

Retailers Selling

Cross Retailer %

35.3%

Price Spread

59.5%

30-Day Price Trend

-1.6%

30-Day Supply Change

+9.9%

Volatility (30d)

0.01

Price Range

Price per carat distribution across retailers

$2,177/ct

10th Percentile

$1,318

Median

$2,177

90th Percentile

$3,773

Score Distribution

1.2K diamonds scored across 4 quality tiers

Excellent

225 (18.6%)

Very Good

263 (21.8%)

Good

317 (26.2%)

Average

403 (33.4%)

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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 24%

Lab-Grown I SI1Same specifications, lab-grown origin

Save 76%

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