Have you ever wondered why some chilis just give a slight tingle while others bring tears to your eyes? The answer lies in the Scoville scale—a fascinating measuring system that puts chili heat into numbers. From mild jalapeños to fiery habaneros: we show you how the science behind the burn works and what capsaicin does to your taste nerves.
Why Do Chilis Burn on the Tongue?
All chilis are spicy—but not equally spicy. Some varieties really make you sweat, while others are rather gentle on the tongue. And that’s exactly where the Scoville scale comes in: it measures how much fire is in a chili. Who’s responsible? A substance called capsaicin.
What Is Capsaicin?
Capsaicin is a chemical compound that is present naturally in chilis and is responsible for their spiciness. It stimulates the heat receptors in our skin, especially in the mucous membranes. That’s why we feel the burning mainly on the tongue and in the throat—much stronger than if we were to rub a chili on our arm. For this reason, you should never touch your eyes with chili hands!
But not all chili pods contain the same amount of capsaicin. Even within one variety, there can be differences. That’s why the Scoville scale never gives an exact value, but always a range. Did you know that a chili’s spiciness depends heavily on environmental factors like climate or soil conditions?
How Is Spiciness Measured?
The American pharmacist Wilbur Scoville made it his task to investigate chili spiciness. He developed an organoleptic analysis for this—a sensory evaluation. Scoville assigned pure capsaicin a spiciness level of 16 million units and created a scale that measures how much you have to dilute the capsaicin until it’s no longer perceptible in taste.
For this analysis, alcohol is used to extract the capsaicin from the chili. Then sugar water is added to the extract so that five test subjects can determine at what point the spiciness is no longer noticeable. Today, science has of course advanced much further: there are more precise quantitative analyses that separate the individual components in the lab.
From Mild to Fiery: The Variety of Chilis
The Scoville scale ranges from zero units for mild bell peppers to several million for the world’s hottest chili varieties. Jalapeños, for example, range between 2,500 and 8,000 Scoville units, while habaneros reach between 100,000 and 350,000 units. Chipotle chilis, the smoked jalapeños, move in a similar range to fresh jalapeños.
With the Scoville Scale You Now Have Practical Orientation
With the Scoville scale, you now have practical orientation on which chilis are hotter and which are milder. The range is enormous: while jalapeños sit at moderate 2,500 to 8,000 Scoville units and habaneros reach between 100,000 and 350,000, the extremes really get serious. The Carolina Reaper held the world record from 2013 to 2023 with up to 2.2 million Scoville units. Since 2023, Pepper X with measured 2.69 million Scoville units is officially the world’s hottest chili—for comparison: pepper spray is around 2 million units.
