An ultrasound device can be calibrated for forming skeleton density information. This ultrasound device includes a calibration program integrated programmatically to the ultrasound device and a calibration part for calibrating a known distance L. The velocity of ultrasound is known for different temperatures in the calibration part. The ultrasound device includes at least two transmitters having a distance of L1 between them for transmitting ultrasound signals into the skeleton, and at least two receivers having a distance of L2 between them for receiving ultrasound signals from the skeleton. At least one of distances L1 and L2 is equal to the calibrated known distance L. The ultrasound device also includes a processing unit for calculating an ultrasound velocity in the skeleton.
