There is provided a method of estimating a location and/or orientation of a handheld personal care device with respect to a user of the handheld personal care device. The method includes obtaining measurements of a posture of a part of the body of the user as the user uses the handheld personal care device. The method also includes using the measurements to estimate the location and/or orientation of the handheld personal care device with respect to the user during use of the handheld personal care device based on a predetermined relationship between the location and/or orientation of the handheld personal care device and the posture of the part of the body of the user. A personal care system, a posture measurement device and a machine-readable medium are also disclosed.
