Electrical Wire Size Calculator and Wire Size Calculation Explained Metric and British

The maximum allowable current of a conductor depends upon the wire size. For a higher diameter of wire size, the conductor can carry more current depending on the conductor material. Similarly, the maximum allowable voltage drop by the wire depends upon the length of the wire. These parameters should be considered while calculating the wire size. Use the online electrical wire size calculator for calculating wire size either in metric (SI) and British system.

The Allowable Voltage Drop of Wire.

When current flows through a wire, heat is produced. A higher current produces a higher heat depending upon the specific resistance of the material and wire size. Even though the resistance of a conductor is very low but still it produces heat and causes a voltage drop. Therefore, for higher current, a high gauge wire is selected to reduce the power loss due to heat and the voltage drop. The maximum allowable voltage drop from a source point to load is 2.5%.

Temperature and Resistance

Due to the collision of charge and the fraction to the current flow, every current-carrying conductor produces heat. While continuous heat generation can add up and cause big problems. For a high-temperature conductor, the current carrying capacity of the conductor decreases. Similarly, a low-diameter wire can produce more heat and vice versa.

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Online Electrical Wire Size Calculator

Total Load, P (Kw)

Voltage, V (v)

Temperature, T (C)

Length of Cable, L (Metric/British)

20% Extra Load

Current, I (A)

Maximum Allowable Voltage Drop, Vd (v)

Actual Voltage Drop, Vd (v) (Metric)

Recommended Cable Size (Metric)

Actual Voltage Drop, Vd (v) (British)

Recommended Cable Size (British)

The electrical wire size calculator uses the following formula for cable size selection in the metric and British systems. The calculator first finds the current with I=P/V. Then it adds the extra 20% of the load for future extensions and it is recommended to set it “Yes”.

After that, the cable size calculator uses to consider the temperature parameter. It may increase or decrease the current by some factor. As the resistance is high at higher temperatures.

Once the current value is final, the online cable size calculator finds an optimal wire size based on the required specification of the current. The recommendation is only for standard copper wires. The wire size is recommended in metric (SI) and British systems.

Then the calculator finds the actual voltage drop in the length of the wire. The parameter of length is a meter for metric and for the British it is feet. The allowable voltage drop in the wire is 2.5% of the source voltage. Check if the actual voltage drop increases than the allowable voltage drop, use a higher cable size.

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