Relationships between the convective turnover time and the rotation period P_sat at which a transition occurs between the saturated and non-saturated regimes of X-ray emission. The convective turnover time is expressed in the scale of Wright et al. (2011). Relationships are shown for stars with initial periods of rotation on the ZAMS ranging from 0.12 to 3.4 days. These relations have been derived assuming a correlation between X-ray emission regimes and rotation sequences using the I and C sequence parameterisation of Barnes (2010). They are compared with the linear relation (continuous thick line) that assumes a transition between X-ray emission regime at a critical Rossby number Ro^sat = 0.30 (G12). The linear relation corresponding to a continuous transition from saturated to non-saturated regime X-ray emission at Ro^sat = 0.13 is shown as a thick dashed line.