An electric toothbrush comprising a toothbrush device (100) and a charge device (200) is operative to provide an accurate determination and an adequate indication of the duty performance of toothbrushing. The toothbrush device (100) comprises a supply unit (110), a control unit (120) and a driving portion (130). The control unit (120) is provided with a time-measuring portion (121) for measuring the duty time during toothbrushing, a pressure-measuring portion (122) for measuring the duty pressure during toothbrushing, a position-determining portion (124) for determining the duty position during toothbrushing and a computing portion (123) to compute a duty performance. An accurate determination of the duty performance is achieved in computing portion (123) which computes the duty performance in response of the duty time, the duty pressure and the duty position. "duty" time, pressure and position being the time, pressure and position during operation of the toothbrush during toothbrushing. The duty performance and optionally the duty time, duty pressure and duty position are indicated by indication portion (2 10) located either on the toothbrush device (100) or on the charge device (200). In case of a detachable toothbrush device (100), the control unit (120) in the toothbrush device (100) and the indication portion (210) in the charge device (200) may communicate via a wireless communication link.