The name of the scale used to measure the spicy heat of peppers is called the Scoville scale.
The Scoville scale is a measurement of the pungency (spicy heat) of chili peppers, as determined by the concentration of capsaicinoids, which are the compounds responsible for the heat. The scale was created by Wilbur Scoville in 1912 and is based on the subjective perception of heat by human testers. The scale ranges from 0 (no heat) to over 2 million (extremely hot), with the jalapeño pepper typically measuring around 2,500–8,000 Scoville units, and the Carolina Reaper, one of the hottest peppers in the world, measuring over 2 million Scoville units.