In 1912, a pharmacist by the name of Wilbur Scoville developed a method to measure the heat level of chile peppers. The pungency is measured in multiples of 100 units from the bell pepper, which rates at zero, to the fire-breathing habanero, which measures in at the highest end of the scale at three hundred thousand. The units of measurement are referred to as “Scoville units” or “Scovilles” and are best described as units of dilution. A chile that rates 1 Scoville unit would take 1 unit of water to negate the heat. For example, it would take 30,000 to 50,000 units of water to neutralize a Tabasco pepper.
These days, many chile lovers use a new system which is referred to as the Official Chile Heat Scale, which rates the heat of chiles from 0 to 10. On this simpler scale, bell peppers still rate as 0 and habaneros rate at the top end of the scale with a 10. Comparatively, jalapenos rate as 5, serranos at 6, and cayennes and Tabascos at 8.
It’s interesting that regardless of the heat rating that a chile may have, everyone’s palate is different and some lower registering chiles will taste hotter to some people than a higher registering chile. For example, an East Indian dish may taste very hot to someone used to Mexican spicing, even though the chiles used measure lower on the heat scale.
Fortunately, most chile lovers are more concerned with flavor than with the heat measurement!