Convert Calories to Attojoules
Convert Calories (cal) to Attojoules (aJ) instantly and accurately.
Conversion Formula
aJ = cal × 4.184000000e+18
About Calories
A calorie (cal) - the thermochemical calorie - is exactly 4.184 J, defined as the heat to raise 1 g of water by 1°C. Standard since 1954. The calorie is the fundamental unit of heat measurement in thermochemistry: glucose combustion releases 669.9 kcal/mol; water vaporisation requires 539.7 cal/g. Bond dissociation energies in quantum chemistry are often quoted in kcal/mol. Note: the dietary Calorie (capital C) on food labels is 1 kcal = 4,184 J - a factor-of-1,000 difference that causes persistent confusion. 1 cal = 4.184 J = 1.163 × 10⁻³ Wh.
About Attojoules
An attojoule (aJ) is 10⁻¹⁸ J - the scale of individual X-ray photons and superconducting qubit circuits. A 1 keV X-ray photon carries 160 aJ; a visible green photon (~550 nm) carries ~0.36 aJ. Josephson junction energies in superconducting qubits are set in tens to hundreds of aJ to achieve quantum coherence at millikelvin temperatures. XRISM's cryogenic TES X-ray spectrometer resolves individual photon energies at the hundreds-of-aJ level with ~7 eV FWHM resolution. 1 aJ = 10⁻¹⁸ J = 6.242 eV.
Quick Reference Table
| Calories (cal) | Attojoules (aJ) |
|---|---|
| 1 cal | 4.184 × 1018 aJ |
| 2 cal | 8.368 × 1018 aJ |
| 5 cal | 2.092 × 1019 aJ |
| 10 cal | 4.184 × 1019 aJ |
| 25 cal | 1.046 × 1020 aJ |
| 50 cal | 2.092 × 1020 aJ |
| 100 cal | 4.184 × 1020 aJ |