Calories (cal) to Kilojoules (kJ) Converter
Enter a value to instantly convert between energy units.
1 Calorie (thermochemical) = 0.0042 Kilojoule
Key Formulas
Kilocalorie → Kilojoule
kJ = kcal × 4.184Kilojoule → Kilocalorie
kcal = kJ × 0.239006Kilowatt-Hour → Joule
J = kWh × 3600000Joule → Kilowatt-Hour
kWh = J × 2.77778e-7Formula
kJ = cal × 0.004184One thermochemical calorie equals 0.004184 kilojoules. Calories (lowercase 'cal') are a legacy unit from chemistry and physics, defined as the energy to heat 1 gram of water by 1°C. Kilojoules are the SI standard and appear on modern scientific equipment and international research papers. Converting calories to kJ is essential when reading historical scientific literature or lab equipment calibrated in the old unit system.
Source: NIST SP 811, Table B.8
Frequently Asked Questions
Real-World Examples
Definition. 1 thermochemical calorie = 4.184 joules = 0.004184 kJ exactly.
1 cal = 0.004184 kJ
A chemistry lab reports 1,000 cal of reaction heat — equivalent to 4.184 kJ for the SI journal submission.
1000 cal = 4.184 kJ
A combustion experiment releases 500 cal of energy — 2.092 kJ recorded in the lab notebook.
500 cal = 2.092 kJ
A calorimeter measures 2,500 cal of heat transfer — 10.46 kJ entered into the equipment's digital display.
2500 cal = 10.46 kJ