You can also choose to fill in the desired characteristic impedance and leave one of the trace parameters blank. Selecting the button next to the blank field will calculate the missing parameter. Equations used to make these calculations are provided at the bottom of this page.
Zo Equation: IPCD317A (Eq. 5.38a) The equation for Co in IPCD317A (Eq. 5.38b) is inconsistent with the equation for Zo (Eq. 5.38a). The equation used here can be derived by multiplying the propagation delay by the characteristic impedance. 
