**How to determine the length of a cable using a ohmmeter**

Multiply the resistance by 20 to find the length of the wire in feet. For example, a reading of 54.6 ´ 20 » 1,100). For a maximum of 1,500 ft., the resistance must measure 75 ohms or less. This formula works for standard 24-gauge phone wire.

**
Cable Lengths and Gauge DC Resistance Chart
**

** 18 Gauge**

78 X ohms = resistance | 51 | 32 | 25 | 12 | 6 | 4 | 2 |

feet | 4,000 | 2,500 | 2,000 | 1,000 | 500 | 300 | 200 |

** 20 Gauge**

50 X ohms = resistance | 80 | 50 | 40 | 20 | 10 | 6 | 4 |

feet | 4,000 | 2,500 | 2,000 | 1,000 | 500 | 300 | 200 |

**22 Gauge**

31 X ohms = resistance | 129 | 80 | 64 | 32 | 16 | 9 | 6 |

feet | 4,000 | 2,500 | 2,000 | 1,000 | 500 | 300 | 200 |

**24 Gauge**

20 X ohms = resistance | 200 | 125 | 100 | 50 | 25 | 15 | 10 |

feet | 4,000 | 2,500 | 2,000 | 1,000 | 500 | 300 | 200 |

**26 Gauge**

12 X ohms = resistance | 133 | 208 | 166 | 83 | 41 | 25 | 16 |

feet | 4,000 | 2,500 | 2,000 | 1,000 | 500 | 300 | 200 |

**
Note: 27 Gauge and above is not recommended.
**