Scoville Heat Units: How Are They Measured?

Scoville Heat Units: How Are They Measured?

This question gets asked a lot by our customers: what exactly are Scoville Heat Units? 

When you shop our pepper seeds by heat level, for example, you'll notice that each one lists its heat in Scoville Heat Units. And depending on what species or type of pepper you want, you might find that one has a lower number of heat units while another can have over a MILLION!

If you haven’t read our page on the Scoville Scale, then head over there first. We explain in further detail what these scales are and where certain peppers fall on the scale, from lowest heat to the highest. 

So how are these units measured, and what kinds of tests do they undergo to get their respective numbers? Keep reading to learn more.

Scoville pepper heat scale graphic

What Are Scoville Heat Units?

Scoville Heat Units, or SHUs for short, measure the heat and pungency of a chili pepper based on its concentration of “capsaicin.” This chemical compound lives in the oils and membranes of all peppers that help give them their unique flavors and heat. The unit itself is actually a measurement of sugar water, which is used to help determine a pepper’s heat level. The more Scoville Heat Units there are, the more amounts of measurable sugar water were needed for testing. This is explained in more detail further below.

These units make up the Scoville Scale, otherwise known as the Chili Heat Scale or the Chili Scoville Scale, which was named after the creator Wilbur L. Scoville. While the process has changed from when peppers were first tested, the Scoville Scale remains the primary indicator of pepper heat to this day.

Photo of Wilbur Scoville


In 1912, W. Scoville worked as a scientist for Parke-Davis, a pharmaceutical company that now lives as a subsidiary of Pfizer. During his time there, he developed the “Scoville Organoleptic Test,” which he used to measure the capsaicin of chili peppers. According to his 1912 article “Notes on Capsicums”, published in the Journal of the American Pharmaceutical Association, he documented his process of testing these peppers:

“The method I have used is as follows: One grain of ground capsicum is macerated overnight in 100 cc. of alcohol. After thorough shaking, filtered. This alcoholic solution is then added to sweetened water in definite proportions until a distinct but weak pungency is perceptible on the tongue.”

This initial process marked the first scientific approach to understanding different types of heat in peppers, as well as having developed a systematic method of labeling this heat in what is now known as the Scoville Scale.

How Are Scoville Heat Units Measured?

Before SHUs, growers determined a pepper’s heat level by simply eating it and making judgments based on their experience. As subjective as this sounds today, this method was the basis for the Scoville Organoleptic Test, which involved multiple taste testers to determine a pepper’s heat level.

organoleptic test used to test pepper heat levels

Scoville Organoleptic Test

As described above, the Scoville Organoleptic Test involves diluting a pepper sample into a measurable sugar water solution. These solutions are prepared ahead of time and are taste-tested by a group of people to determine if they feel any heat. If the test subjects feel heat with the sample, then the process is repeated. With each repetition, another measurement of sugar water, or Scoville Heat Unit, is added to further dilute the sample. This continues until the majority of test subjects do not feel any more heat when tasting their samples.

To put it into perspective, a sweet bell pepper has a heat level of 0 SHUs. This means that no amount of sugar water solution was used to remove the heat from this pepper. In other words, sweet bell peppers contain zero heat. The Jalapeno pepper, on the other hand, contains an average heat level of 2,500 SHUs. This means that test subjects sipped 2,500 diluted solutions of jalapeno pepper samples before they felt no more heat. That’s a LOT of samples to get through!

And let’s not forget about the Carolina Reaper, whose heat level sits at a maximum of 2,200,000 SHUs.


This test served as the primary way of determining the Scoville heat units of peppers around the world for years. However, the Scoville organoleptic test has been scrutinized for its proneness to subjectivity. Human subjects will have varying degrees of sensitivity to a pepper’s heat, which can skew the results of the final pepper’s heat level. This also affects the number of samples human testers can take within a certain amount of time. After consuming so many peppers with varying degrees of heat, taste testers may feel burnt out – quite literally!

High-Performance Liquid Chromatography test graphic from Shimadzu

High Performance Liquid Chromatography Test

For a more accurate and objective approach to measuring Scoville heat units in chili peppers, the High-Performance Liquid Chromatography (HPLC) Test was developed.

In this process, scientists dry and grind up a pepper sample before they extract the chemical components that make the pepper’s heat. Once this is done, they pump the sample through an HPLC column at a very high pressure that separates the chemical components. Meanwhile, a detector analyzes these components and translates them into a chromatogram scientists use to determine not only how hot the pepper is, but also the number of individual capsaicinoids the pepper contains.

In other words, it’s a whole lot of science.

What’s great about using HPLC tests is their ability to minimize subjectivity. These tests completely analyze every aspect of a pepper’s heat, which leaves little room for error. The results from these tests have been consistent: the New Mexico State University Chile Breeding and Genetics Program, one of the leading pepper testing sites in the world, analyzed over 5,000 samples and have come up with consistent and reliable results.


While HPLC tests sound great and easy to do, they cost more than organoleptic tests or other types of heat tests. Using hi-tech machines to basically tear apart a dried pepper costs a lot of money to do. Plus, if you want to conduct these types of heat level tests, then you must find a laboratory that regularly tests these with the proper equipment to do so.

lab assistant inserting pepper sample through the HPLC column

Which Pepper Heat Tests Should I Do?

If you cross-breed pepper strains to come up with new versions of superhot peppers, then test these new strains to get certifiable results. Most growers send in samples of new pepper strains that were intentionally or accidentally created in their plots to get more information out of them. Certain indicators of new pepper strains include different physical attributes of the pepper itself, its plant leaves, or its flowers, as well as a unique flavor or aroma. (CAUTION: Testing the flavor of new pepper strains can be dangerous, especially when the heat level is unknown.)

Not all pepper growers need to test their peppers, especially if a heat level or heat range has been identified for the strain that they are growing.

To choose which test to conduct on a pepper sample, compare the pros and cons of each before settling on an option:

Pepper Heat Tests

Scoville Organoleptic Test

High Performance Liquid Chromatography Test

·         Costs Less

·         More Time

·         Allows Fewer Tests to be Done

·         Less Objective; More Subjectivity

·         Can do On Your Own (Unofficial Testing)

·         Costs More

·         Less Time

·         Allows More Tests to be Done

·         Less Subjectivity; More Objective

·         Can do At a Science Testing Lab (Official Testing)


How to Have Scoville Hat Unit Tests Done

Several laboratories across the country conduct both certified organoleptic and HPLC heat tests on chili peppers to determine their number of SHUs. These tests normally cost around $65 to conduct, but make sure to verify the cost as each lab may differ. For a certified Scoville heat unit test, reach out to the following laboratories. They take submissions from the public and usually provide confidential test results within two weeks.

Depending on where you are, you may have to ship your peppers to the research lab. Labs may have certain shipping requirements, so make sure to investigate them. Normally, they ask to ship them fresh or in powder form. For powder, the rule of thumb is the finer the powder, the better the results.

Guinness World Records Testing

Getting tests done to achieve a world record takes a little more effort than just regular testing. Guinness World Records has its own Guidelines Pack for anyone looking to achieve specific records, including:

  1. A signed statement of authentication from a suitably qualified person (i.e. a horticulturalist)
  2. The plant has been correctly identified by species and/or variety
  3. HPLC tests done at a certified lab
  4. Plant growing details must be provided
  5. 2 Witness Statements from independent individuals

Be sure to keep up with any changing guidelines to these requirements.

Want to grow the next hottest pepper in the world? Check out our growing tips and grab yourself a pack of superhot pepper seeds to get started today!

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