Thermochemical, International Table and 15 degree calories in joules, with a 2,000 kcal day costed in each and the spread between them.
| Definition | Joules per calorie | Status | Where you meet it | Kilojoules in 2,000 kcal | Gap versus thermochemical |
|---|---|---|---|---|---|
| Thermochemical calorie (cal_th) | 4.184 | exact by definition | chemistry, nutrition and the food Calorie | 8,368.0 | +0.0000% |
| International Table calorie (cal_IT) | 4.1868 | exact by definition | steam tables and older mechanical and HVAC engineering | 8,373.6 | +0.0669% |
| 15 degree calorie (cal_15) | about 4.1858 | measured, sources differ | classical calorimetry, now largely historical | 8,371.6 | +0.0430% |
The three calorie definitions, with a day's intake worked out in each by UnitGlide, reusable under CC BY 4.0.