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Power Calculations
Power (P) = Current (I)^2 * Resistance (R)
Power (P) = Voltage (V) * Current (I)
Power (P) = Voltage (V)^2 / Resistance (R)
Resistance Calculations
Resistance (R) = Power (P) / Current (I)^2
Resistance (R) = Voltage (V) / Current (I)
Resistance (R) = Voltage (V)^2 / Power (P)
Voltage Calculations
Voltage (V) = Current (I) x Resistance (R)
Voltage (V) = Power (P) / Current (I)
Voltage (V) = sqrt(Power (P) x Resistance (R))
Current Calculation
Current (I) = Power (P) / Voltage (V)
Current (I) = sqrt(Power (P) / Resistance (R))
Current (I) = Voltage (V) / Resistance (R)
If you’re looking for which wire size to use based on your current draw, or how to size wire in general have a look at our full “What Size Wire Should I Be Using?” Article.
Our Spec 44 Wiring guide is also below:
Wire Size | Use Case | Current Rating (When Bundled) | Wire Size (mm²) | Diameter(mm) Including Insulation |
| 24AWG | Sensor wiring | 4A | 0.35 | 1.0 |
| 22AWG | Sensor wiring, small injectors, coil triggers, relay triggers | 6A | 0.74 | 1.2 |
| 20AWG | Sensor wiring, injectors, engine actuators (VVT solenoids etc), coil triggers, and lights (30w) | 8A | 0.8 | 1.4 |
| 18AWG | Small fans, pumps, coil pack power, motors (wiper/window), and lights (55w) | 11A | 1.3 | 1.6 |
| 16AWG | Fans, transfer/vacuum pumps, and lights (100w) | 16A | 1.7 | 1.8 |
| 14AWG | Medium duty fuel pumps, and small radiator fans | 17A | 2.6 | 2.2 |
| 12AWG | Heavy duty fuel pumps, and large radiator fans | 21A | 4.2 | 2.7 |
| 10AWG | Power distribution, and electric power steering pumps | 28A | 6.6 | 3.9 |
| 8AWG (1000V) | Power distribution | 55A | 15.2 | 5.2 |
| 6AWG (1000V) | Power distribution | 70A | 23.9 | 6.4 |
| 4AWG (1000V) | Power distribution | 95A | 38.0 | 7.8 |
