# How to Convert Amu to Joule ••• Creatas/Creatas/Getty Images

An atomic mass unit, or amu, is one-twelfth of the mass of an unbound atom of carbon-12, and it used to express the mass of atomic and subatomic particles. The joule is the unit of energy in the International System of Units. Understanding of the relationship between the binding energy and the mass defect in Albert Einstein's Theory of Relativity equation clarifies the process of converting amu into joules. In the equation the mass defect is the “vanishing” mass of the protons and neutrons that is converted to energy that holds the nucleus together.

## Conversion 1 amu into joule

Remember that the mass of a nucleus is always less than the sum of the individual masses of the protons and neutrons that compose it. In calculating the mass defect use the full accuracy of mass measurements, because the difference in mass is small compared to the mass of the atom. Rounding off the masses of atoms and particles to three or four significant digits prior to the calculation will result in a calculated mass defect of zero.

Convert the atomic mass unit (amu) into kilograms. Remember that 1 amu = 1.66053886*10^-27 kg.

Write down Einstein's formula for the binding energy \"?E\": ?E = ?m_c^2, where \"c\" is the velocity of light that is equal to 2.9979_10^8 m/s; \"?m\" is the mass defect and equals 1 amu in this explanation.

Substitute the value of 1 amu in kilograms and the value of the velocity of light in Einstein's equation. ?E= 1.66053886_10^-27 kg_(2.9979*10^8 m/s) ^2.

Use your calculator to find ?E by following the formula in Step 4.