This device for painlessly measuring the distance from where an instrument sits in the canal of a tooth to the apex or hidden end of a tooth is used prior to a root canal procedure. The design enhanced usability by including a large, easy-to-read visual interface with a tilting mechanism that can eliminate glare from the display surface. Another innovation is the satellite remote display, which can be positioned near the patient's mouth and allows the doctor to keep his eyes in one area rather than looking back and forth.