We present an algorithm that automatically computes the QT interval duration from body surface electrocardiograms (ECGs). The algorithm consists of three processing steps: (1) PQ junction detection, (2) optimal lead selection, and (3) T-wave end detection. A previously developed algorithm for QRS detection was employed to detect the onset of each QRS complex, which was taken to be the PQ junction time. In the lead selection step, the ECG lead with the largest T-wave was automatically picked by the algorithm. For the T-wave end detection, the ECG signal in the estimated T-wave portion was transformed by means of an ECG curve length transform (LT); the T-wave end was determined using the resultant LT signal. The algorithm was applied to the first 30 seconds of 532 records in the PTB Diagnostic ECG Database. A score of 29.66 was achieved, which represents the RMS difference between the reference QT intervals and the algorithm’s results.