Is the airport capacity related to number of runways?
Airport Capacity

At major airports the capacity of the system of runways is the most restricting element. While it is usually possible to increase capacity of the other airport elements or adding a new runway (plus associated taxiways) is very expensive and takes a very long time to complete.

The runway capacity is the principal cause of most extreme instances of delays that lead to widespread schedule disruptions, flight cancellations and missed flight connections. The runway capacity varies greatly from day to day and changes are difficult to predict (even a few hours in advance).

Factors:

The capacity of the runway system depends on several factors, the most important ones:


Mix of aircraft classes using the airport: the aircraft mix indicates composition of aircraft fleet that is using any particular runway (e.g. 25% S, 60% L and 15% H).
Separation requirements imposed by the ATM system: due to wind tip vortices, leading aircraft and trailing aircraft must be separated by a determined distance (Heavy aircraft are the ones that produce more wake turbulence).
Type and location of exits from the runway: trailing aircraft of any pair cannot touch down on the runway before leading aircraft is clear of the runway. High-speed runway exits (also well placed runway exits) reduce runway occupancy times for arriving aircraft.
Mix of movements on each runway and the sequencing of the movements: specified for all combinations of consecutive operations (arrival-departure). There's an important trade-off between maximum arrival and departure rates that an airport can achieve.
Lateral separation: (especially in bad weather) between aircraft approaching the same airport on parallel runways.
Sequencing and separation of departing and landing aircraft on runways that intersect.
Sequencing of aircraft approaching airports located in close proximity to one another, where one aircraft must cross the path of another aircraft landing at a nearby airport.
Direction and strength of winds.
Noise-related and other environmental considerations and constraints.


Conclusion:

It is difficult to predict the capacity of the runway system of an airport, so it is difficult to compare two airports with similar runway characteristics, since the factors depending on the airport capacity involve different design and operational parameters. Furthermore, everything is subject to the important probabilistic factor, the weather, which makes the prediction and comparison of airport capacity even more difficult.