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Cable Length Calculator

Calculate Cable Wire Spool Length Using a Resistance Calculation & an Ohmmeter

This is a basic wire length calculator to get you into the range of how much insulated cable is remaining on a spool. This form of wire length calculation can only be used for 2 or 4 lead insulated wire, and for wire gauge from 12 to 30.

NOTE: another method used to measure cable/wire on a spool is to cut a length of wire. Weigh it; then weigh the spool using the piece of wire you measured as your multiplier. For example. Lets say you cut off an 10' length of wire and it weights 1 pound. You weigh the spool and it weighs 780 pounds. The approximate length of the cable would be 7,300' assuming the cable reel weighs 50 pounds.


  • Use an ohmmeter to measure the resistance of the length of wire.
  • Enter the resistance into the space below.
  • Select the wire gauge on the calculator below.
  • Click the "Calculate Cable Length" button.

Enter Resistance: (ohms) Enter Wire Gauge: AWG)

Approximate Cable Length equals:

  • 2 conductor wire length is between: ___ and ___ feet ( ___ to ___ meters)*
  • 4 conductor wire length is between: ___ and ___ feet ( ___ to ___ meters)

*When measuring 2 conductor wire, it is assumed 0.2 ohms of lead resistance. 4 conductor wire measurement will be more accurate.


TIP: For improved speed and exceptional accuracy, use this Cable Length Meter. The Cable Length Meter can be used on a single strand insulated cable from 26 to 4/0 AWG (250 to 500 MCM). Measuring Length: 15? to 30,000? (5 to 9144 Meters).

The UEI CLM100b Cable Length Meter is an excellent tool to measure spooled or wound insulated cable/wire. Built solid and supplied with a Ruggedized boot for reliable performance in the field. Currently being utilized by major utility companies, electrical contractors, wholesalers, installers any many others to get quick inventory calculations or measurements to account for the amount of wire/cable installed in a given period, job or day. It is very accurate and easy to use. Simply attach the Kelvin Clips to both ends of the cable. Adjust the indicator to the size wire you are measuring and that's it. A temperature compensation circuit ensures accuracy by compensating for the temperature of the wire.


  • Large 4 digit LCD display with enunciators
  • Measures copper and aluminum cable in feet and meters (covers the major wire types)
  • Easy to use and calibrate & low battery indicator
  • Auto power off (after being idle after 15 minutes)
  • Automatic temperature compensation
  • Milliohm measurement capability
  • User calibration mode (calibration standard included)
  • Identifies high-resistance connections
  • Automatic Temperature Compensation


Wire Size: 26 to 4/0 AWG (250 to 500 MCM)
Measuring Length: 15’ to 30,000’ (5-9144M)
Operating Temp Range: 32˚to 104˚F (0˚ to 40˚C)
Operating humidity: 20 to 80% RH
Length Accuracy:
(Nominally, dependent on wire gauge and length;
see manual for chart)

< 300' at 65˚ to 75˚F: ± (1% of reading + 3')

< 300' at below 65˚ and above 75˚F: ± (2% of reading + 3')
> 300' at 65˚ to 75˚F: ± (1% of reading)
> 300' at below 65˚ and above 75˚F: ± (2% of reading)

Resistance Range:

0 to 10Ω: (± 0.5% of reading + 3 LSD*)

10 to 99.99Ω: (± 0.5% of reading + 10 LSD*)

*LSD = Least Significant Digit

Resolution: 0.5' (0.1m Length) | 1mΩ resistance
Power: 9 volt battery
Battery life: Typically 60 hours (180 hours in Sleep Mode). Extended measurements can lower battery life to no less than 12 hours.


  • 2 (easy-to-attach) Kelvin Clips on pre-calibrated leads (approx 4' long)
  • 2 copper calibration bars for automatic calibration & an abrasive pad to remove oxidation
  • Rugged carrying case, battery, ruggedized boot with clips & owners manual
  • 5 year limited manufacturer's warranty

Download Owner's manual (PDF 550kb)

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