This paper introduces an enhanced (bootstrapped) method for tracked ultrasound probe calibration. Prior to calibration, a position sensor is used to track an ultrasound probe in 3D space, while the US image is used to determine calibration target locations within the image. From this information, an estimate of the transformation matrix of the scan plane with respect to the position sensor is computed. While all prior calibration methods terminate at this phase, we use this initial calibration estimate to bootstrap an additional optimization of the transformation matrix on independent data to yield the minimum reconstruction error on calibration targets. The bootstrapped workflow makes use of a closed-form calibration solver and associated sensitivity analysis, allowing for rapid and robust convergence to an optimal calibration matrix. Bootstrapping demonstrates superior reconstruction accuracy.