CPACS has no attributes for units. Values are given in SI units or in units derived from them, and the documentation of each element names its unit in square brackets at the end, e.g. [m], or [-] for a dimensionless value. Values from aviation practice are converted accordingly: a cruise altitude of FL350 (35000 ft) is written as 10668, a speed of 250 kt as 128.61. The base units are:
| Unit | Quantity |
| [m] | length, position, distance |
| [kg] | mass |
| [s] | time |
| [K] | temperature |
| [A] | electric current |
Derived units are, for example:
| Unit | Quantity |
| [m^2], [m^3] | area, volume |
| [m/s] | velocity |
| [N] | force |
| [Nm] | moment |
| [N/m^2] | pressure, stress |
| [J], [W] | energy, power |
Angles are the exception: they are given in degrees [deg], which are easier to read than radians. Where an element uses another unit, e.g. radians for a phase angle or radians per second for a rotational rate, its documentation says so, and the unit stated there applies.