Reading Rapaport
The Rapaport Diamond Report is the most widely referenced price sheet in the diamond trade. Published weekly, it sets a baseline that buyers and sellers use to anchor negotiations. When someone quotes a price as "Rap minus twelve," they mean twelve percent below the number on this sheet. Understanding how the sheet is organized — and what its numbers actually represent — is the first step toward reading any diamond price with confidence.
How the grid works
The Rapaport sheet is a set of grids, one per weight range. A grid for 1.00–1.49ct stones is separate from the grid for 1.50–1.99ct stones. Each grid covers a single shape category — round brilliants have their own sheets, and fancy shapes (oval, pear, cushion, emerald, and others) have a separate set.
Within each grid, columns represent color grades running left to right from D (colorless) through M and beyond. Rows represent clarity grades running top to bottom from IF (internally flawless) through I3. The cell where a color column meets a clarity row contains a number — the Rapaport price for that combination, expressed in hundreds of US dollars per carat.
A cell reading 72 means $7,200 per carat. A cell reading 135 means $13,500 per carat. Every value on the sheet is per carat, not per stone.
Reading a price
To find the Rapaport price for a specific stone, follow three steps.
First, select the correct grid by matching the stone's weight to a weight range and its shape to round or fancy. A 1.52ct round goes to the round 1.50–1.99ct grid. A 0.91ct oval goes to the fancy 0.90–0.99ct grid.
Second, locate the cell. Find the stone's color grade along the top and its clarity grade down the side. The intersection is the per-carat Rapaport price in hundreds of dollars.
Third, calculate the total. Multiply the cell value by 100 to convert to dollars, then multiply by the stone's carat weight. If the cell reads 85 and the stone weighs 1.52ct, the Rapaport value is $85 × 100 × 1.52 = $12,920.
Notice that a 0.99ct stone and a 1.00ct stone with identical color and clarity land on different grids. The 1.00–1.49ct grid carries higher per-carat values than the 0.90–0.99ct grid, which is why crossing a "magic number" threshold — 0.50, 1.00, 1.50, 2.00 — creates a price jump that has nothing to do with quality. This is the weight interaction described in the previous lesson.
Discounts and premiums
The Rapaport sheet is a reference point, not a transaction price. Almost no stone trades at exactly the listed value. Instead, the trade quotes prices as a percentage off (or, less commonly, above) the sheet.
A price quoted as "minus 15" or "–15 back" means 15% below Rapaport. If the sheet says $10,000 per carat, the asking price is $8,500 per carat. A quote of "+2 ask" means 2% above the sheet — rare, but it happens for exceptional stones or when demand spikes in a specific category.
The size of the discount depends on the stone, the market, and the moment. A well-cut GIA-graded round in a popular size might trade at Rap –5. The same specifications with weaker proportions or a less recognized lab certificate might trade at Rap –25. Regional differences add another layer: a stone that moves at –10 in one market might sit at –18 in another where demand for that category is softer.
This is why experienced traders pay less attention to the absolute Rapaport number and more attention to where discounts are trending. A narrowing discount — say, from –15 to –10 over a few weeks — signals strengthening demand even if the sheet price stays flat.