Transformer Wire Size Calculator

Introduction: The Transformer Wire Size Calculator is an essential tool for electricians and individuals involved in transformer installations. This calculator simplifies the process of determining the appropriate wire size for transformers, considering load voltage, load current, maximum wire length, and desired voltage drop. Proper wire sizing is crucial to minimize voltage drop and ensure safe and efficient power transfer.

Formula: The recommended wire size is calculated using the formula: (2 * Load Current * Max Wire Length * Voltage Drop) / Load Voltage. The result is rounded up to the nearest whole number to provide a practical wire size in American Wire Gauge (AWG).

How to Use:

  1. Enter the load voltage of the transformer in volts.
  2. Input the load current in amperes.
  3. Enter the maximum allowable wire length in feet.
  4. Specify the desired maximum voltage drop as a percentage.
  5. Click the “Calculate” button to obtain the recommended transformer wire size in AWG.

Example: If the load voltage is 240 volts, the load current is 10 amperes, the maximum wire length is 50 feet, and the desired voltage drop is 3%, enter these values into the calculator, click “Calculate,” and the result will provide the recommended wire size in AWG.


  1. Q: Why is wire sizing important for transformers? A: Proper wire sizing ensures minimal voltage drop, efficient power transfer, and compliance with safety standards.
  2. Q: Can I use this calculator for different types of transformers? A: Yes, this calculator is suitable for various transformers. Ensure that specific transformer characteristics are considered for accurate results.
  3. Q: What is the significance of the 2 multiplier in the formula? A: The multiplier accounts for both the outgoing and return conductors, providing a more accurate wire size recommendation.
  4. Q: How does voltage drop affect the choice of wire size? A: Voltage drop impacts the efficiency of power transfer. Choosing a wire size that minimizes voltage drop ensures optimal performance.
  5. Q: Can I exceed the recommended wire size for extra safety? A: While safety is crucial, exceeding the recommended wire size may lead to unnecessary costs. It’s advisable to follow the calculated size closely.

Conclusion: The Transformer Wire Size Calculator is a valuable resource for optimizing electrical installations and ensuring the proper selection of wire sizes for transformers. Use this calculator to determine the recommended wire size based on load characteristics, maximum wire length, and desired voltage drop, promoting energy efficiency and system reliability.

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