Scoville Heat Units (SHU) refer to the way the heat of a chilli is measured. While a mild chilli such as an Anaheim will have a SHU rating of approximately 1500, the Carolina Reaper (the current record holder for the hottest chilli in the world) peaks at approximately 2,200,000 SHU. Scoville heat units measure the concentration of capsaicinoids, of which capsaicin is the predominant component. The more capsaicin, the hotter the chilli.


This scale for measuring the pungency of chillies is named after its creator, American pharmacist Wilbur Scoville, whose 1912 method is known as the Scoville Organoleptic Test. This test used a weight of dried chilli dissolved in alcohol to extract the heat components or capsaicinoids. This was then diluted in a solution of sugar water. A panel of five trained testers were given decreasing concentrations of the extracted capsaicinoids until a majority (at least three) could no longer detect any heat in the dilution. The heat level was then based on this dilution, rated in multiples of 100 SHU.

This test was obviously very subjective and has been replaced by the High-Performance Liquid Chromatography Test (HPLC), which measures the concentration of heat-producing capsaicinoids, with capsaicin content as the main measure. The results are then converted to SHU.

How We Use SHU on Our Heat Scale