Hallo Sushil,

I will have to consider the pin capcitance of the microcontroller and the load, but what about the copper tracks on the PCB? What if we use a general purpose board + wires (or a bread board) do the stray capacitance calculations differ now?

Copper traces have a capacitive and an inductive component. Capacitance of copper traces can be very easily estimated by the help of formula of parallel plate capacitor, when copper traces run over a ground plane. Then a 0.3mm wide copper trace running on top layer of 1.6mm thick PCB, while having a ground plane on bottom side, gives a capacitance to ground of less than 1pF per 10cm. Compared with 3pF of typical input capacitance of 74HCMOS gate (10pF maximum) you see, that capacitance of copper trace is not the dominating factor.
With a four layer PCB, capacitance of copper trace is three times higher.
With single layer PCB or even single wires, on the other hand, capacitance to ground cannot be estimated very well, because stray capacitance to other copper traces and wires is heaviliy increased and plays a much more important role. With the result, that effective capacitance to ground cannot be easily predicted. Although capacitance to ground of copper traces is mostly a bit smaller than when using double sided PCB with massive ground plane, this is no benefit at all. Big stray capacitance means that all copper traces are affecting each other, which is not good! Here a massive groundplane leads to a screening of all traces against each other. Stray capacitance between different copper traces of PCB and cross coupling of signals is heaviliy decreased.

Following a rule of thumb inductive component of copper trace or single wire is about 1nH per mm, when not running over ground plane. When there's a groundplane very close to copper trace inductivity is drastically decreased, the more the closer the distance is. Use of massive groundplane guarantees that inductive coupling between different copper traces of PCB is heaviliy minimized. So, the use of at least double sided PCB with massive groundplane should be your standard, when you work with mcu!!!!!!!

Unfortunately, 'capacitance' and 'inductivity' is not enough to understand behaviour of copper trace when very fast slewing signals are running over it. Electrodynamics comes into play, and characteristic impedance Z of transmission line has to be considered. With L = 100nH / 10cm and C = 1pF / 10 cm from our rough estimation we get a characteristic impedance of Z = SQRT(L/C) = 316 Ohm.
Transmission line effects can only be neglected, when copper traces are rather short (less then about 20cm for 74HCMOS series). Then, following rule of thumb is valid: When your pull-up resistor is much bigger than Z, then your copper trace looks like a capacitance.

Now you should be able to estimate how much copper trace capacitance contributes.

Kai