Wire Ampacity Reference

About the Wire Ampacity Reference

Provides a quick reference for the typical ampacity (current rating) of common copper conductor sizes at 60°C/75°C, for planning purposes.

How to use this calculator

1. Choose the wire gauge or size you want to check, such as \(12\) AWG or \(10\) AWG.
2. Read the typical ampacity value for copper wire under standard conditions.
3. Compare that value to the current your circuit will draw, measured in amperes \(\\text{A}\).
4. If the needed current is close to or above the reference value, choose a thicker wire or check the installation conditions.

The formula explained

This tool does not use one single formula, it looks up typical ampacity values for common copper wire sizes. The result tells you the approximate safe current rating for a given wire gauge under standard conditions.

• \(\\text{AWG}\) = American Wire Gauge, the wire size system used for common electrical wire
• \(\\text{A}\) = amperes, the unit of electric current
• \(\\text{ampacity}\) = the maximum current a wire can safely carry
• \(\\text{copper}\) = the conductor material the reference values are based on

Step by step method

1. Identify the wire size, for example \(14\) AWG, \(12\) AWG, or \(10\) AWG.
2. Look up the typical ampacity for that size in the reference table.
3. Compare the load current to the wire's ampacity, and keep the load below the safe value.
4. If the wire will be in a hot place, bundled with other wires, or used over a long distance, choose a larger wire because real-world conditions can lower safe ampacity.

Worked example

Problem. A circuit will draw \(18\) \(\\text{A}\). What wire size should you check first among common copper sizes?

1. A \(14\) AWG copper wire is typically rated around \(15\) \(\\text{A}\), so it is too small for \(18\) \(\\text{A}\).
2. A \(12\) AWG copper wire is typically rated around \(20\) \(\\text{A}\), so it is a better match for \(18\) \(\\text{A}\).
3. The wire chosen should have ampacity at least as high as the expected current, so \(12\) AWG is the safer reference choice here.

Tips and common mistakes

• Ampacity depends on insulation type, temperature, bundling, and installation method, so a table value is only a starting point.
• Bigger wire number means thinner wire, so \(14\) AWG is smaller than \(12\) AWG, and smaller wire usually has lower ampacity.

Frequently asked questions