How to Calculate a Rapaport Discount (With Examples)
Diamond traders rarely quote a price in dollars straight away. They quote a discount (or premium) to the Rapaport list, for example "minus 35" or "35 back". This guide shows how to turn that into a real price.
What the Rapaport list is
The Rapaport Price List gives an asking price per carat for a round or fancy-shape diamond of a given weight range, colour and clarity. Prices on the sheet are written in hundreds of US dollars per carat, so a figure of 72 means US$7,200 per carat.
Almost nobody trades at the full list price. The market price is expressed as a percentage below (or, for rare goods, above) the list.
The formula
- Net price per carat = Rap list price × (1 + discount ÷ 100)
- Stone total = net price per carat × carat weight
A discount is written as a negative number. "Minus 35" is −35%, so you pay 65% of the list price.
Worked example
A 1.00 ct stone with a list price of US$7,200 per carat, offered at −35%:
| Step | Calculation | Result |
|---|---|---|
| Net per carat | 7,200 × (1 − 0.35) | US$4,680 |
| Stone total | 4,680 × 1.00 | US$4,680 |
The same quality at 1.52 ct, from a different weight bracket with a list price of US$9,800 per carat, offered at −28%:
| Step | Calculation | Result |
|---|---|---|
| Net per carat | 9,800 × (1 − 0.28) | US$7,056 |
| Stone total | 7,056 × 1.52 | US$10,725.12 |
Common mistakes
- Using the wrong weight bracket. The list price jumps at weights such as 0.90, 1.00, 1.50 and 2.00 ct. Always use the bracket of the actual weight.
- Mixing up the sign. A premium (+5) means you pay more than list; a discount (−5) means less.
- Forgetting currency. Rap prices are in US dollars. If you settle in rupees, dirhams or baht, convert the stone total at the day's rate, not the per-carat price before rounding.
Doing it faster
You can try the numbers in our free Rapaport discount calculator. In E-Ratna, every stone carries its Rap price and discount, and the pricing engine lets you revise a whole lot, a shape or a size range in one step, so your prices keep up with the market.
