What is the Scoville Scale?

If you’re a chili head (or even if you’re not!), you’ve probably heard a lot about the Scoville Heat Scale. It has been the standard way to measure the heat in hot peppers for over 100 years. But a lot of people don’t fully understand what the scale actually is. The basic principle of the Scoville Heat scale is pretty simple to understand: the bigger the number on the Scoville scale, the hotter the pepper. But if you really want a more thorough understanding of this scale, there is plenty to learn!

The History of the Scoville Scale

The scale was created by American Wilbur Scoville back in 1912. This scale coincides with Wilbur Scoville’s method for testing heat called the Scoville Organoleptic Test. Scoville was a chemist who used his knowledge and his love for spicy food to develop the test. Originally, the test was meant to aid Scoville’s work in the pharmaceutical industry.

At the time, he was employed by the Detroit-based pharmaceutical company Perke-Davis. When Scoville worked for this company, it was the largest pharmaceutical company in America. The company produced a pain-reliever called Heet liniment, which contained capsaicin from hot peppers. Scoville needed a way of measuring the amount of capsaicin in peppers in order to ensure that every package of Heet liniment had the appropriate amount of this active ingredient, so he created the heat scale that we still use today (more on that later!)

Scoville had a successful career aside from his work with hot peppers. He was a professor for a few years at the Massachusetts College of Pharmacy. He also won several awards in the pharmaceutical field and even wrote two books. His first reference book, The Art of Compounding, is still highly regarded within the pharmaceutical field. But the average person will recognize Wilbur Scoville’s name for his namesake test.

How the Scale Works

In its early days, the Scoville Heat Scale was based on the opinion of panelist members. Usually, there were five panelists, and each one of them was experienced in tasting (and tolerating) the extreme heat of hot chili peppers. The testing started with weighing and drying whatever type of pepper was being ranked. Testers dissolved this dried pepper using alcohol. From this substance, the pepper’s capsaicin could be easily extracted. Capsaicin is the source of every hot pepper’s heat. When you feel and taste the burn, that’s the capsaicin.

Next, the tester dilutes the capsaicin with sugar water. After each dilution, the panelists taste the capsaicin. As long as the panelists are able to taste the heat, they keep diluting the capsaicin with more sugar water. Once the heat is completely gone for the majority of the panelists (usually three out of five), they stop adding sugar water. This is the number of Scoville Heat Units contained in that pepper. Every dilution equals one Scoville Heat Unit or SHU for short.

What is Capsaicin?

Capsaicin is found in all hot pepper and is especially concentrated in a hot pepper’s seeds and inner flesh. This compound irritates people and animals alike, producing a burning sensation. The more capsaicin is in a substance, the more pungent the heat.

Putting Peppers into Perspective

So, what do all these numbers actually mean in the real world? Bell peppers don’t have any capsaicin and, thus, they measure zero SHU on the Scoville scale peppers. On the opposite end of the spectrum, police-grade pepper spray is slightly more diluted than pure capsaicin, but it’s still hotter than any currently-known hot pepper. Police carry pepper spray that can measure up to 5,300,000 SHU.

Pure capsaicin measures 16,000,000 SHU. It must be diluted 16,000,000 times before the heat goes away! The only known substance that is hotter than pure capsaicin is resiniferatoxin, which measures nearly ten times hotter than pure capsaicin—it measures 15,000,000,000 SHU! You can find this substance in cactus-like plants in Morocco and parts of Nigeria.

If you go further down on the scale, you’ll find the milder peppers. For example, the jalapeno has an average Scoville rating of 5,000 SHU. The Poblano measures 1,250 SHU, and sweet peppers, on average, measure between 100 and 500 SHU. Individual pepper’s measurements on the Scoville Heat Scale will vary. Not every pepper of the same species will have one standard measurement of SHU. But every type of pepper has its own range of SHU and an average SHU.

The Top 10 World’s Hottest Peppers on the Scoville Scale

Every, Guinness World Records puts out a list of the Top 10 World’s Hottest Peppers. Since new hot peppers are constantly being discovered and cultivated, this list is constantly changing. Currently, these are the top-ranking Scoville scale peppers.

1. Pepper X -- hottest: 2.693 million Scoville Heat Units (SHU)
2. Carolina Reaper—hottest: 2,200,000 SHU, average: 1,641,000 SHU
3. Trinidad Moruga Scorpion—hottest: 2,009,231 SHU
4. 7 Pot Douglah—hottest: 1,853,936 SHU
5. 7 Pot Primo—hottest: 1,469,000 SHU
6. Trinidad Scorpion, aka Butch T—hottest: 1,463,700 SHU
7. Naga Viper—hottest: 1,349,000
8. Ghost Pepper, aka Bhut Jolokia—hottest: 1,041,427 SHU
9. 7 Pot Barrackpore (tied)—hottest: 1,000,000 SHU
10. 7 Pot Red, aka the Giant (tied)—hottest: 1,000,000 SHU
11. Red Savina Habanero—hottest: 500,000 SHU

Using the Scale Today

The Scoville Heat Scale is not without its controversy. Not everyone thinks it’s the most reliable way to measure spicy foods since every person (and thus every panelist) will have different taste buds. When one person can no longer detect heat, another might still be able to. People also build up a tolerance to capsaicin over time and become less susceptible to its burn. This makes the Scoville scale subjective.

Scoville vs. HPLC

For these reasons, many have turned to a more precise scientific method for determining a pepper’s hotness. With High-Performance Liquid Chromatography (HPLC), you can obtain the same knowledge as with the Scoville scale, but it’s more accurate and consistent. Every liquid substance can be broken down with HPLC into its different components. Even though the methodology behind HPLC is different from Wilbur Scoville’s test, you still measure the peppers using Scoville Heat Units. Even if a pepper is tested using HPLC, it gets a SHU number. Whether it’s Scoville or HPLC, it’s always helpful to know what you’re getting into before you take a bite of something spicy.

If you have a taste for the spicier things in life, it helps to have a working knowledge of the Scoville scale. If you’re not able to take the heat, the Scoville scale helps you avoid scorching peppers. But if you’re a hot pepper enthusiast, Scoville gives you something to brag about!

Interest in the Scoville Scale Over Time | Google Trends