Scoville scale
The standard measure of chilli pungency, devised in 1912 and now based on chemical measurement.
Also: Scoville heat units, SHU, Wilbur Scoville, chilli heat scale
The Scoville scale was devised by American pharmacist Wilbur Scoville in 1912. His test diluted a chilli extract in sugar water until a panel of tasters could no longer feel the heat, and the dilution factor became the rating. Modern labs use high-performance liquid chromatography to measure capsaicinoids directly and convert to Scoville heat units. Pure capsaicin scores about 16 million. Bell peppers rate zero, jalapeños 2,500 to 8,000, cayenne 30,000 to 50,000, habanero 100,000 to 350,000, and the hottest cultivars such as the Carolina Reaper over a million. Ratings vary with growing conditions, so they are guides, not guarantees.