Diamond Price Calculator
Total price from carat and price per carat.
Calculate a diamond's total price from its carat weight and price per carat, and see how the per-carat rate jumps at magic sizes.
From comparable certified stones of the same colour, clarity and cut. It varies by more than an order of magnitude, which is why it is an input.
Total price
$6000
1.00 ct at $6000/ct
Per-carat rates step up sharply at the round weights, because demand concentrates there. A stone just under a magic size is visually indistinguishable and commonly 15 to 25% cheaper per carat — so the total saving is far more than the weight difference suggests.
How the Diamond Price Calculator works
Diamonds are priced per carat, and the total is simply weight times that rate — but the rate itself is not constant. It steps up sharply at the round numbers, so a 1.00 carat stone can cost 20% more per carat than a 0.95, and therefore far more than 5% more in total. Buying just under a magic size is the single most reliable way to save money on a diamond.
Also known as: price per carat calculator · diamond cost estimator
Why the per-carat rate is not constant
Diamonds are priced per carat and the total is weight times that rate, which is trivial arithmetic. The complication is that the rate itself depends on the weight, and not smoothly.
Prices step up at the round weights — 0.50, 0.75, 1.00, 1.50, 2.00 — because demand concentrates there. Cutters lose money producing a 0.98 carat stone when a slightly less well proportioned 1.01 is worth substantially more per carat, so they cut for the magic sizes and the supply below them thins.
The practical consequence is that a 0.95 carat stone is visually indistinguishable from a 1.00 and commonly costs 15 to 25% less per carat, which makes the total saving far larger than the five percent difference in weight.
A worked example
A 1.00 carat stone at $6,000 per carat is $6,000. A 0.95 carat of identical colour, clarity and cut at a 15% lower rate is $5,100 per carat, or $4,845.
That is a saving of over $1,100 for a stone 0.15 mm narrower — a difference nobody detects without a loupe and a gauge. The same logic applies at every magic size, and the effect is strongest at 1.00 and 2.00.
Where the answer misleads
The calculator deliberately does not supply a per-carat rate, because there is no useful average. Colour, clarity, cut, fluorescence and certification move the rate across more than an order of magnitude, and a figure baked in would be wrong for almost every stone. Take the rate from comparable certified stones.
Certification matters more than most buyers expect. The same physical stone graded by different laboratories can carry grades two steps apart, and prices follow the certificate rather than the stone. Comparing a rate from one lab's stones against another's is comparing different things.
Finally, lab-grown diamonds follow the same per-carat arithmetic on a completely different and rapidly moving price curve. Comparing lab and natural rates directly tells you very little.
Frequently asked questions
How is a diamond's price calculated?
Price per carat multiplied by the carat weight. A 1.20 carat stone at $6,000 per carat is $7,200. The complication is that the per-carat rate depends on the weight itself as well as on colour, clarity and cut.
What are magic sizes?
The round weights — 0.50, 0.75, 1.00, 1.50, 2.00 — where per-carat prices jump because demand concentrates there. A 0.95 carat stone is visually indistinguishable from a 1.00 and commonly costs 15 to 25% less per carat.
Why does this calculator not know the price per carat?
Because it depends on colour, clarity, cut, fluorescence, certification and the market on the day, across a range spanning more than an order of magnitude. Any figure baked in would be wrong for almost every stone. Take the rate from comparable certified stones.
Do lab-grown diamonds price the same way?
The same per-carat arithmetic, at very different rates, and the rates have fallen quickly. Lab and natural stones should be compared on their own markets rather than against each other.