https://doi.org/10.1351/goldbook.C00784
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.