As seen in the tkn::tkmeasure class, tkn offers the possibility to convert some measure into different units
Currently, tkn handles three unit types: Energy, Time en Lenght. Few other units are included in tkn but that cannot be converted

The available energy units are the following: eV, keV, MeV, GeV, TeV
The available time units are the following: as, fs, ps, ns, us, ms, s, min, h, d, y
The available lenght units are the following: am, fm, pm, nm, um, mm, cm, m

In general, units can be converted only in the scale of a same type. One exception is given for the energy to time conversion. For very low lifetimes, it is common to express the width of a level in energy. This conversion is taken into account in tkn.