1ct I SI1 Round Natural Diamond Price
The median is $3,073. Half of these diamonds are listed between $2,572 and $3,697 at 25 retailers (measured on October 29, 2026), and the same stone is often priced very differently at each.
1ct I SI1 Round Natural Diamond Price has a median price of $3,073, with the middle half listed between $2,572 and $3,697, across 2077 certificated stones from 25 retailers on Carat Hunter (measured on October 29, 2026).
What it actually costs
Middle half listed between $2,572 to $3,697
The same stone, priced differently
Across 1403 stones of this specification carried by more than one retailer, the dearest listing sits 87% above the cheapest for the identical diamond, a typical gap of $2,406. This is not a difference in the stone. It is the same certificated diamond, and the gap is what you avoid by comparing before you buy.
What changes the price
Median price for the same specification with one attribute changed, so you can see what flexing each one is worth.
| Change | Median | Difference |
|---|---|---|
| Carat 0.75ct | $1,554 | -49% |
| Carat 1.5ct | $6,609 | +115% |
| Clarity SI2 | $2,718 | -12% |
| Clarity VS2 | $3,468 | +13% |
| Colour J | $2,692 | -12% |
| Colour H | $3,845 | +25% |
| Origin lab-grown | $942 | -69% |
Reading this specification
At SI1, inclusions are visible under 10x magnification and eye-cleanliness is not guaranteed. In round cuts this is worth checking stone by stone rather than assuming, because two diamonds with the same grade can look quite different.
I sits at the warm end of near-colourless. It reads white face-up in most round brilliants, and it pairs especially well with yellow or rose gold, where the metal supplies the warmth the eye expects.
A round brilliant returns more light than any other cut and hides both warmth and small inclusions better than a step cut, so grades that would be marginal elsewhere are usually safe in this shape.
The 87% spread on this specification is unusually wide, which means the retailer you choose matters more than any single grade on the report.
A lab-grown stone of this exact specification runs about 69% below the natural equivalent. If the origin is not important to you, that is the single largest saving available on this page.
Stepping up to 1.5ct costs about 115% more. Buying just under a round carat weight is the usual way to capture most of the visual size without paying the full jump.
Dropping to 0.75ct saves about 49%, and the difference in visible diameter is small enough that most people cannot pick it without the two stones side by side.
Stones at this specification now
Current examples carried by more than one retailer, so the price comparison is real.
- 1.01ct I SI1from $2,087 across 11 retailersAs of October 28, 2026
- 1.11ct I SI1from $2,000 across 8 retailersAs of October 29, 2026
- 1.13ct I SI1from $2,231 across 12 retailersAs of October 29, 2026
- 1.07ct I SI1from $2,117 across 12 retailersAs of October 29, 2026
- 1ct I SI1from $2,248 across 13 retailersAs of October 29, 2026
- 1ct I SI1from $2,246 across 7 retailersAs of October 26, 2026
FAQ
What is a fair price for a 1ct I SI1 Round Natural diamond?
The median is $3,073 and the middle half of stones are listed between $2,572 and $3,697 (measured on October 29, 2026). Those figures cover 2077 certificated diamonds listed by 25 retailers, so anything materially above the upper figure is worth questioning.
How much do retailers differ on the same diamond?
Across 1403 stones of this specification carried by more than one retailer, the typical gap between the cheapest and dearest listing of the identical diamond is 87%, or about $2,406.
What is the cheapest way to change this specification?
Moving to 0.75ct lowers the median by 49% to $1,554. Moving to SI2 lowers the median by 12% to $2,718. Moving to J lowers the median by 12% to $2,692.
How many retailers carry 1ct I SI1 Round diamonds?
Carat Hunter tracks 25 retailers actively offering diamonds matching this specification, across 2,468 distinct certified stones.
Is Natural pricing typical for 1ct Round diamonds?
Natural diamond pricing holds its premium over lab-grown at equivalent specifications. The premium varies by shape and clarity grade.
How this is measured
Measured on October 29, 2026 from 2468 certificated diamonds between 1 and 1.14 carat, carrying 15384 current listings across 25 retailers. Each stone with a recently confirmed price contributes the cheapest price we last saw for it, so the distribution reflects what a buyer comparing retailers would actually pay. These figures summarize many stones, so they carry the day they were measured rather than the date of any one listing.
Certificated stones with a current listed price only, and every price figure uses only prices we confirmed recently. Uncertificated inventory is excluded because its grades cannot be verified against a laboratory report.
Updated October 29, 2026. Aggregate data across 25 retailers.