The Scoville Scale is a heat map for chili peppers and quickly gives you an idea of a chile pepper’s heat in relation to other chiles.

It was created to identify the exact capsaicin level of common chiles, and it’s usually shown in table form, something like this:

Capsaicin is the active component in chili peppers and gives them their distinctive heat, or spiciness. Pure capsaicin is at the top of the chart with 15 M units as you can see.

Each of those mexican peppers is accompanied by their Scoville range.  Technically it’s usually a range for each chile even when growing conditions can affect the exact heat level it is a usefull guide.

Notice how Poblano peppers are quite mild by nature?   Most people don’t know that because they are such large peppers.

And note that Serranos are twice as hot as Jalapenos — good to know right?

You’ll also notice that chiles tend to get hotter as they get smaller — this is a great tip to keep in mind and will give you a quick reference point when you come across new chile varieties.  Another way of saying it is that small chiles tend to have higher levels of capasicin concentration.

For example, these little Habanero beauties are some of the hottest peppers you’ll come across in Mexican cuisine:

Here’s a look at some common Mexican dried chiles and their accompanying Scoville Heat Units. As you can see there is no variation when a chile is dried.

If there is a recipe that uses a pepper that has a high heat level this scale can be used to identify which chili is the ideal for you. And substitute.