How Do You Calculate The Resistance Of Copper Wire?
There is a specific formula to use to calculate the resistance of copper wire based on its area and length. For those who are weak in math, a calculator will come in handy. The area of electrical wire is measured in a unit called “circular mils.” This number is needed to calculate a wire’s resistance. To get this information for your particular project, you will need to look it up in the “National Electrical Code Handbook NFPA 70,” Chapter 9, Table 8. An electrical code pocket reference, electrical or instrumentation textbook may also have the same information. From a reliable source, such as a code reference book, look up the cross sectional area for the gauge wire you are seeking to calculate. If the wire size is followed by “mcm” or “kc mil,” just add three zeros behind the number. What you might see for #10-gauge and 500-mcm size wire: #10-gauge = 10,380 circular mils 500-mcm = 500,000 circular mils Measure the length of the wire in feet, rounding to the nearest foot. If the wire
