The Wire Gauge for Safe Voltage Drop calculator computes the lightest (highest number) gauge of wire for a circuit to NOT drop below a percent threshold due to line-loss over a circuit.
INSTRUCTIONS: Choose units and enter the following:
- (cL) Circuit Length
- (C) Current (amps flowing through the circuit)
- (V) Circuit Volts (e.g. 220V or 110V)
- (DL) Voltage Drop Limit (acceptable %, e.g., 5%)
- (WT) Wire Type (solid copper, stranded copper, solid aluminum, stranded aluminum)
- (TR) Temperature Range: normal (77o - 121oF) or high (122o - 167o F)
- (P) Single or Three Phase
Wire Gauge (WG): The calculator returns the lightest (highest number) gauge of wire that will carry the current and NOT have a line loss of voltage greater that the user entered percent. The calculator also returns the cross-section area for the chosen guage in square millimeters (mm2) and the diameter in millimeters (mm).
The Math / Science
Lighter gauge wire is less expensive and often easier to work with. However, lighter gauge wire (higher numbered) can have an unacceptable effect on the drop of voltage over the length of the circuit. Maintaining voltage is important since many pieces of equipment will wear out more quickly if the voltage is below a margin which is often 5% or 10%. The factors in voltage drop include the length of the circuit, guage of wire, current (amps), wire type and material, temperature range and whether the circuit is single or three phase. This calculator lets the user specify these criteria and iterates through the characteristics of the wire gauges to find the lightest (highest guage) that sustains the voltage to within the required percentage drop. You could do this by hand, and compute the voltage drop for different wire gauges over the length you need, but this calculator does that for you rapidly.
This answers the question, "What gauge of wire do I need for my voltage not to drop more than 5%?" This formula returns the lightest gauge wire that does not exceed the voltage drop, and it provides the predicted voltage drop within the threshold. VIDEO INSTRUCTIONS
The Voltage Drop formula is:
VD = (K * P * L * C)/(A)
where:
- VD = Voltage Drop
- K = K factor for materials
- P = Phase Constant
- L = Length of the wire
- C = Current
- A = Cross-section area of the wire.
The type of wire and temperature range are used to compute the K factor (Ohms - circular mils per foot).
- K = 11 for Solid and stranded copper in the normal temperature range
- K = 12 for Solid and stranded copper in the high temperature range
- K = 18 for Solid Aluminum in the low temp range, and K = 20 for Solid Aluminum in the high temp range.
- K = 19 for Stranded Aluminum in the low temp range, and K = 20 for Stranded Aluminum in the high temp range.
The gauge is used to look up the wire cross-section area in circular mils. Phase is used to choose a phase constant (P), where P = 2.0 for single phase and P= 1.732 for 3 phase.
Usage
The user should measure the length of the run, and then choose the phase (single or 3), and the wire type and gauge. Pull-down menus are given for gauge, wire type, phase and temperature range.
The voltage drop can have an adverse affect on equipment. Typically, a 2% drop is the maximum acceptable drop in local use
Note that significantly higher volts can be used without affecting the voltage drop. This results in a lower percentage drop in comparison. For this reason, long lines from power stations to cities are typically in extremely high voltages and reduced for normal consumption via transformers after the distance has been run.
Wire Guage Information
In the United States, wire gauges for electrical service are typically measured using the American Wire Gauge (AWG) system. The gauge of the wire determines its diameter, which in turn affects the amount of current it can safely carry.
Here are some common wire gauges used in residential and commercial electrical service:
Residential Wiring:
- 14 AWG:
- Used for lighting circuits and other low-load circuits.
- Typically connected to 15-amp breakers.
- 12 AWG:
- Used for general-purpose outlets and lighting circuits.
- Typically connected to 20-amp breakers.
- 10 AWG:
- Used for heavy-duty appliances like water heaters and air conditioners.
- Typically connected to 30-amp breakers.
- 8 AWG:
- Used for large appliances such as electric ranges and dryers.
- Typically connected to 40-50 amp breakers.
- 6 AWG:
- Used for larger appliances and subpanels.
- Typically connected to 50-60 amp breakers.
- 4 AWG:
- Used for subpanels, large appliances, and service entrance wiring.
- Typically connected to 70-100 amp breakers.
Commercial Wiring:
- 3 AWG:
- Used for commercial lighting and power circuits.
- Typically connected to 100-amp breakers.
- 2 AWG:
- Used for large commercial appliances and subpanels.
- Typically connected to 100-125 amp breakers.
- 1 AWG:
- Used for large commercial services and subpanels.
- Typically connected to 125-150 amp breakers.
- 1/0 AWG (0 AWG):
- Used for main service entrance wires in commercial buildings.
- Typically connected to 150-175 amp breakers.
- 2/0 AWG (00 AWG):
- Used for large commercial service entrance wiring.
- Typically connected to 175-200 amp breakers.
- 4/0 AWG (0000 AWG):
- Used for very large service entrance wiring, particularly in large buildings.
- Typically connected to 250-300 amp breakers.
Special Applications:
- Grounding Wires: Often use 6 AWG or larger, depending on the requirements of the electrical service.
- Service Entrance Cable: Larger cables like 2/0 AWG to 4/0 AWG are used for the service entrance to supply the main electrical panel.
The specific gauge required depends on the current (amperage) of the circuit and the distance the wire must run. Always follow the National Electrical Code (NEC) and local regulations for safety and compliance.
Europe Wire Gauges
Wire gauges are not the same in Europe as they are in the United States. Europe generally uses the metric system for wire sizing, rather than the American Wire Gauge (AWG) system used in the U.S..
Key Differences:
- Measurement System:
- United States (AWG): Wire size is measured using the American Wire Gauge (AWG) system, where a higher gauge number indicates a thinner wire and a lower gauge number indicates a thicker wire.
- Europe (Metric System): Wire size is typically measured by the cross-sectional area of the wire in square millimeters (mm²). The diameter of the wire may also be noted.
- Common Wire Sizes in Europe:
- 1.5 mm²: Commonly used for lighting circuits.
- 2.5 mm²: Commonly used for general power outlets and small appliances.
- 4 mm²: Used for larger appliances or circuits with higher current demands.
- 6 mm²: Used for high-demand appliances like ovens or electric showers.
- 10 mm²: Used for very high-demand circuits and connections to the main distribution board.
- 16 mm² and larger: Used for main service lines and heavy-duty applications.
- Electrical Standards:
- European countries follow different electrical standards, such as the IEC (International Electrotechnical Commission) standards.
- The wiring regulations and standards may vary slightly between countries but are generally more uniform across the European Union.
Conversion Between Systems:
There's no direct one-to-one conversion between AWG and metric sizes, but rough equivalents can be determined:
- AWG 14 ≈ 2.08 mm²
- AWG 12 ≈ 3.31 mm²
- AWG 10 ≈ 5.26 mm²
However, the closest metric sizes used in practice might be 1.5 mm², 2.5 mm², 4 mm², and so on.
When working across different regions, it's important to understand these differences and ensure that the appropriate wire size is used according to local codes and standards.
Electrician Calculators
- Voltage Drop: This computes the voltage drop in volts and as a percentage over a length of cable (wire) based on length of wire, gauge, wire material, temperature range and phase.
- Wire Gauge Choice for Safe Voltage Drop: This determines the lightest gauge of wire that can be used over a run (circuit) that maintains adequate voltage.
- Circular Mils and Voltage Drop: This computes voltage drop based on wire diameter in circular mils instead of wire gauge.
- Electricity Usage Cost: This computes the cost of electricity for the use of a piece of equipment based on the power consumption rate, duration and cost of electricity.
- Electricity Consumption: This computes the amount of electricity consumed by an electrical appliance or motor over time.
- Rolling Offset: This computes the travel (T) and run (R) of a rolling offset used in conduit piping based on the offsets and angles.
- Diameter of AWG Wire: This provides the diameter of wire based on the American Wire Guide (AWG) gauge in mils and millimeters, and it also provide the cross-section area in square millimeters.
- P = V2 / R: This computes power (Watts) based on the voltage (V) and resistance (R).
- DC to AC Converter: Computes the approximate voltage of Alternating Current (AC) from the voltage of Direct Current (DC).
- Diameter to Circular Mils: Computed the circular mils of a wire and the cross-section area based on the wire's diameter.