Estimate diamond value or the required base price per carat from weight, color, clarity, cut, shape, certification, selling fees, and resale assumptions.
Diamond Value Formula
The calculator starts with a current neutral price per carat and then adjusts it for the selected stone characteristics:
V = W * P * F1 * F2 * F3 * F4 * F5
To find the neutral base price per carat needed to support a target value, the same equation is rearranged:
P = V / (W * F1 * F2 * F3 * F4 * F5)
Variables:
- V is estimated stone value
- W is stone weight in carats
- P is neutral base price per carat taken from a relevant market comparable
- F1 through F5 is the selected quality, treatment, origin, cut, certification, and demand multipliers
The base price per carat is intentionally user-supplied because gemstone prices change with the market and with the stone’s size bracket. Use a recent comparable that matches the stone type and intended value level, then apply only adjustments that can be supported by a grading report or careful inspection. The result panel also shows an indicative range, a quick-sale reference, and estimated net proceeds after selling costs.
Diamond Value Adjustment Reference
The table summarizes the benchmark and the range available in each adjustment. Multipliers are applied together, so avoid double-counting the same quality feature in the base comparable and again in the selectors.
| Adjustment | Benchmark selection | Available multiplier span |
|---|---|---|
| Color grade | H–I (benchmark) | 0.62× to 1.45× |
| Clarity grade | SI1 (benchmark) | 0.52× to 1.55× |
| Cut quality | Good (benchmark) | 0.65× to 1.18× |
| Shape / demand | Oval / emerald / cushion | 0.82× to 1.15× |
| Certification and origin | Natural, independent report | 0.14× to 1.08× |
Example Problems
Example 1: Estimate the value of a 1.20-carat natural diamond.
Assume a neutral comparable price of $4,000 per carat and a combined multiplier of 1.32 after color, clarity, cut, shape, and certification adjustments:
V = 1.20 * 4000 * 1.32 = $6,336.
Example 2: Find the base price per carat required to support an $8,000 estimate for a 1.50-carat stone with a combined multiplier of 1.20:
P = 8000 / (1.50 * 1.20) = $4,444.44 per carat.
Frequently Asked Questions
Does this calculator use live diamond prices?
No. It deliberately asks for a base price per carat so you can use a current comparable that matches natural versus lab-grown origin, weight range, and market. The quality controls then adjust that baseline consistently.
Why is the result a range instead of one exact price?
Two stones with the same headline grades can differ in proportions, fluorescence, transparency, certification, and buyer demand. A range is more honest than implying that a formula can replace a grading report and comparable inventory.
Should I use retail price or resale price per carat?
Use a base rate that matches your purpose. Retail comparables estimate replacement or shopping value; completed resale or dealer-bid comparables are better for estimating what an owner may actually receive.
