Fluorescence Impact Calculator

Diamond fluorescence is the glow -- usually blue -- a stone gives off under UV light, and how the trade prices it depends heavily on the diamond's Color Grade. This calculator applies a market-convention adjustment table, not a fixed law of physics: for colorless D-F stones, buyers have historically treated fluorescence as a discount factor, since in rare cases it can give the stone a faint hazy or oily look, and the discount grows with fluorescence intensity, from about -1% at Faint up to a 10-12% cut at Very Strong Blue on D-E (F tops out at an 8% cut). For lower color grades from I through K+, the same blue fluorescence can work the other way -- it can visually counteract the diamond's own yellow tint, which is why some buyers pay a small premium for Medium fluorescence on an I, J, or K+ stone (and Strong fluorescence on J or K+) rather than discounting it.

Fluorescence Grade and Color Grade jointly determine the Price Impact result -- the impact table is keyed on both, and which one moves the number more depends on where you are in the table: at low fluorescence the percentage barely moves regardless of color, while at Strong or Very Strong fluorescence, color grade can shift the result by as much as fluorescence grade does. Base Price per carat and Carat Weight only scale the dollar amounts (Adjusted $/ct and Adjusted Total) up or down -- they have no bearing on the Price Impact percentage itself, which comes entirely from the fluorescence-and-color lookup. Because fluorescence pricing is a matter of buyer perception and market convention rather than a graded optical defect, treat the percentages here as a negotiating reference point, not an appraisal.