The Scoville scale measures the degree of pungency of a chili. These chilies contain capsaicin, the chemical which stimulates the chemoreceptor nerve, responsible for the sense of pain. The number of Scoville heat units (SHU) indicates the amount of capsaicin present.

The scale is named after the American scientist
W. Scoville, who developed a test and scale for rating the pungency of chili peppers.

Take for example, bell pepper, which has SHU of zero has no pungency at all. The hotter habanero, with capsaicin of 200,000 SHU would require its extract to be diluted 200 000 times its capsaicin to become undetectable, or become not pungent.

Pungency values stated on the Scoville scale, are imprecise, due to variations in the capsaicin level within a species, as a result of changes in climate, soil; inaccuracy factor inherent in the measurement methods.

Spice heat is now measured by a more accurate method using high performance liquid chromatography.

Savory prawn fritters

Braised tofu

Sweet and sour pork with capsicum,

Variety	Picture	Picture	Scoville unit
pure capsaicin			15 000 000- 16 000 000
police pepper spray			5 000 000
self-defense spray			2 000 000
hottest chili - naga jolokia or bhut jolokia			1 001 000
dorset naga pepper			923 000
red savina pepper			350 000 -   580 000
scotch bonnet			100 000 -   325 000
red habanero			150 000
Jamaican hot pepper , rocoto			100 000  -  200 000
African birdseye			100 000 -   150 000
Thai prik, chiltepin pepper			60 000 -   100 000
super chili pepper			40 000 -     50 000
cayenne long pepper			30 000 -     50 000
tabasco pepper			30 000 -     50 000
aji pepper			12 000 -     30 000
Serrano pepper			10 000 -     23 000
Hot Wax Pepper			5 000 -     10 000
Jalapeno Pepper			2 500 -       8 000
Guajilla Pepper			2.500 -       5 000
Pasilla Pepper			1 000  -      2 000
Ancho Pepper			1 000  -      2 000
Anaheim Pepper , cherry			500 -      2 500
Nu Mex Pepper			500 -      1 000
Santa Fe Grande Pepper			500 -         700
Pimiento Pepper			100 -         500
Bell Pepper , sweet banana			0