The Transmission Line Tool on Mobile (TLTM) Ruling Span Sag Calculator performs quick calculation of mid-span sag as well as three-wave return time with known conductor tension and unit weight. This tool provides users with a mobile approach to checking conductor sag/tension conveniently, or to estimating conductor sag for clearance consideration in preliminary design, when being away from any computing tools or internet connection other than a mobile device. This Calculator does not intend to replace engineering stringing chart report issued for construction.

The Calculator reports sags in accordance with ruling span concept. The conductor profile is modeled with catenary equation which is approximated by using the first two terms of the Maclaurin's infinite series. This approach provides adequate accuracy for variety of span ranges.