A device for drilling holes in bone and configured to determine bone screw length, the device comprising: a surgical power drill comprising: a housing in which a motor and a spindle driven by the motor are accommodated, wherein the spindle has a longitudinal axis and comprises a chuck for clamping a drill bit ; a measuring device releasably attached or fixed to the housing , wherein the measuring device is configured to measure the distance (x) covered by the housing in the direction of the longitudinal axis and relative to a surface of an implant or a bone during a drilling process; and a processing unit to record the distance (x) covered by the housing in the direction of the longitudinal axis and relative to a surface of an implant or a bone with respect to time; characterised in that: the processing unit comprises one or more differentiators to determine at least the first and second derivatives of the distance (x) covered with respect to time at any instant and to record at least a graph of the highest derivative with respect to time; the processing unit further comprises a peak detector to analyze one or more peaks occurring in the graph of the highest derivative with respect to time; and wherein the measuring device comprises a laser device or an ultrasound position sensor for displacement assessment. a surgical power drill comprising: a housing in which a motor and a spindle driven by the motor are accommodated, wherein the spindle has a longitudinal axis and comprises a chuck for clamping a drill bit ; a housing in which a motor and a spindle driven by the motor are accommodated, wherein the spindle has a longitudinal axis and comprises a chuck for clamping a drill bit ; a measuring device releasably attached or fixed to the housing , wherein the measuring device is configured to measure the distance (x) covered by the housing in the direction of the longitudinal axis and relative to a surface of an implant or a bone during a drilling process; and a processing unit to record the distance (x) covered by the housing in the direction of the longitudinal axis and relative to a surface of an implant or a bone with respect to time; characterised in that: the processing unit comprises one or more differentiators to determine at least the first and second derivatives of the distance (x) covered with respect to time at any instant and to record at least a graph of the highest derivative with respect to time; the processing unit further comprises a peak detector to analyze one or more peaks occurring in the graph of the highest derivative with respect to time; and wherein the measuring device comprises a laser device or an ultrasound position sensor for displacement assessment. the processing unit comprises one or more differentiators to determine at least the first and second derivatives of the distance (x) covered with respect to time at any instant and to record at least a graph of the highest derivative with respect to time; the processing unit further comprises a peak detector to analyze one or more peaks occurring in the graph of the highest derivative with respect to time; and wherein the measuring device comprises a laser device or an ultrasound position sensor for displacement assessment. <EOS>