On a nutrition label, when a food says it has 200 "calories," how many scientific (gram) calories is that?

200 nutrition-label "Calories" = 200,000 scientific calories (200 kilocalories), which is about 836,800 joules (about 837 kJ).

Why: two different units share the name "calorie."

• The scientific small calorie (cal), or gram calorie: the energy to raise 1 gram of water by 1 degree C. By the thermochemical definition, 1 cal = exactly 4.184 J.
• The food/large Calorie (Cal), or kilogram calorie: the energy to raise 1 kilogram of water by 1 degree C. 1 Cal = 1,000 cal = 1 kilocalorie (kcal) = 4,184 J.

Nutrition labels use the large Calorie. The convention is to capitalize it ("Calorie") or write "kcal," but most US labels just print "Calories" with no further distinction. So the "200" on the label is 200 kcal.

Conversion:

• 200 Cal x 1,000 = 200,000 small (scientific) calories
• 200 kcal x 4,184 J = 836,800 J, about 837 kJ (this is why EU/Australian labels list around 837 kJ alongside or instead of the Calorie figure)

Quick rule of thumb: multiply the label number by 1,000 to get scientific calories, or by about 4,184 to get joules.</answer>

Sources:

• https://en.wikipedia.org/wiki/Calorie
• https://www.britannica.com/science/calorie
• https://www.healthline.com/nutrition/kcal-vs-calories
• https://public-health.uq.edu.au/article/2023/08/calories-and-kilojoules-how-do-we-know-energy-content-food-and-how-accurate-are-labels