Non-SI unit of energy. There are three differently defined calories: @T06311@ (\(\text{cal}_{\text{th}} = 4.184\ \text{J}\)), international steam table calorie (\(\text{cal}_{\text{IT}} = 4.1868\ \text{J}\)), \(15\ ^{\,\unicode{x26ac}}\text{C}\) calorie (\(\text{cal}_{15} = 4.1855\ \text{J}\)), however only the symbol \(\text{cal}\) is usually used.
Green Book, 2nd ed., p. 112 [Terms] [Book]
PAC, 1996, 68, 957. (Glossary of terms in quantities and units in Clinical Chemistry (IUPAC-IFCC Recommendations 1996)) on page 964 [Terms] [Paper]