Systems and methods are described herein to calculate implant orientation measurements of an acetabular cup implant in hip replacement surgery, such surgery performed with minimally invasive incisions. Surgeons may obtain real-time updated implant orientation measurements that compensate for pelvic tilt of a patient, such tilt measured pre-operatively. Implant orientation measurements may be measured from the patient's anterior pelvic plane, supine coronal plane, standing coronal plane or any other reference plane that the surgeon may find useful. Also disclosed are systems, methods and devices to measure hip center of rotation and provide leg length and offset measurements in hip replacement surgery.