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For transonic wing designs one of the most important elements in the analysis of aerodynamic performance is the evaluation of wave drag. A common technique for estimating the wave drag of a wing consists in summing the contributions at spanwise sections over the wing. The contribution at each section may be evaluated using methods derived from an exact two-dimensional analysis involving the flow conditions just upstream of the shock wave.1;2 For each section of the wing, the equivalent two-dimensional flow conditions are then evaluated from the three-dimensional flow conditions using simple sweep theory. The major drawback of such a method is the need for data coming from the three-dimensional flow state around the wing through experimental measurements or full three-dimensional compressible flow state calculations. Such an approach turns out to be not very useful in the context of preliminary concept design, where expensive three-dimensional compressible flow evaluations are to be avoided, where possible, during design optimization. Thus, to reduce the computational cost of wing wave drag evaluation in preliminary design, approximate methods that do not require expensive three-dimensional flow state calculations may be adopted.