How is the load capacity of a single pile calculated?

Pile capacity Qu = Qp + Qs - W, where Qp = end bearing (Ap*qp), Qs = shaft friction (As*fs), W = pile weight. For end bearing: qp = Nc*c (clay) or Nq*sigma'v (sand). For shaft friction: fs = alpha*cu (alpha method for clay) or K*sigma'v*tan(delta) (beta method). Static methods use soil parameters; dynamic methods use driving data. Load testing (static or dynamic) provides actual capacity. Factor of safety typically 2.0-3.0 applied depending on determination method reliability.