Methods and apparatus to determine a capacity for a network topology are disclosed herein. An example method is described, which includes receiving a network layer topology comprising a plurality of network layer links, applying weights to the network layer links, selecting one of a plurality of traffic elements, the selected traffic element comprising endpoint nodes and a traffic demand, determining, for one or more of the network layer links, whether the selected traffic element may be routed on the network layer link without adding capacity to the network layer link, applying penalties to the weights associated with the network layer links that cannot support the selected traffic element without adding capacity, determining, based on the weights and penalties of the network layer links, a routing path including one or more of the network layer links between the endpoint nodes, adding the selected traffic element to the network layer links on the routing path, and determining the capacity of the network layer links based on the selected traffic element.