An exploration of spiciness invariably leads to the Scoville scale: the method used to determine the heat of the world's chile peppers, including everyday varieties such as bell peppers and jalapeños, and record-breaking types like Carolina Reaper and Pepper X. This heat unit measurement system is the key to understanding the potency and nuances of chile peppers.

At its core, the Scoville scale measures perceived spiciness or pungency in peppers and chiles, specifically those falling within the Capsicum genus. The scale primarily focuses on measuring capsaicinoids, including capsaicin, which are responsible for the fiery sensation experienced when consuming these peppers. Where a higher perceived capsaicin level means a higher ranking on the Scoville heat units (SHU) scale.

Wilbur Scoville, an American pharmacist, dreamt up the Scoville scale back in 1912. The traditional method involves diluting a solution containing chile samples with sugar water until trained tasters no longer discern any heat. This degree of dilution is represented in Scoville heat units. For instance, mild bell peppers have zero SHU, while spicier Thai chiles go from 50,000 to 100,000 SHU. With this exponential scale, "mild hot" chiles register a SHU double than that of "mild" chiles and so forth.

Today's standard method for measuring chile heat is high-performance liquid chromatography, providing a more objective count of individual capsaicinoids present in dried and ground chile peppers.

The Guinness World Records crowned Pepper X as the spiciest of all chiles in 2023. This heat record holder was bred by Ed Currie, the owner of PuckerButt Pepper Company and South Carolina’s hot pepper grower. Pepper X, with an average SHU of 2.69 million, outshone its predecessor, Carolina Reaper, another creation of Currie's, that averaged 1.57 million SHU. The Dragon's Breath chile, although not officially tested by the Guinness World Records, has been reported to contain Scoville heat units as high as 2.48 million.

The Scoville scale remains a useful reference tool for kitchen enthusiasts and professionals alike, especially for those working with chilies regularly. Say, for instance, you are replacing jalapeños with serrano peppers in your cooking, keep in mind that serrano peppers can have over twice the SHU of jalapeños. Plan your measurements appropriately to get the heat level just right.

To aid in determining the heat of your favorite chilies, consult the guide below:

Mild (0 to 2,000 SHU): Bell pepper, Ancho poblano, Lombardo, Anaheim, Golden Greek pepperoncini

Mild Hot (2,000 to 50,000 SHU): Jalapeño, cayenne, arbol, Fresno, serrano, tabasco, lemon drop

Hot (50,000+ SHU): Thai peppers, chiltepin, Charleston, pequín, Rocoto

Spicy Hot (100,000+ SHU): Scotch bonnet, Pimenta de Neyde, Jamaican yellow

Very Hot (250,000+ SHU): Habanero, Fatalii yellow, Red Devil’s Tongue

Really Hot (500,000+ SHU): 7 Pot Yellow, 7 Pot Bubblegum, Red Savina

Fiery Hot (1 million+ SHU): Ghost pepper/Bhut Jolokia, 7 Pot Lucy, Naga Viper, Komodo Dragon

Extreme Hot (1.5 million+ SHU): Carolina Reaper, Trinidad Moruga Scorpion, 7 Pot Dougash