Equipment Grounding Conductor Size Calculator

An equipment grounding conductor size calculator records whether a selected conductor has enough cross-sectional area compared with a required area already established from a reviewed source. It produces an Area margin in kcmil and an Area margin percentage.

The calculation supports grounding-conductor documentation after the applicable grounding-conductor requirement has been identified. It can be used during submittal review, feeder or branch-circuit design review, as-built verification, procurement checks, or PDF worksheet documentation.

The result does not select an AWG or kcmil equipment grounding conductor from a standards table. The required value must be entered from the applicable reviewed table record, design note, specification, engineering calculation, or other approved project source.

Selected and Required Area

The worksheet compares these inputs:

Input	Electrical use
Selected conductor area	The kcmil area represented by the equipment grounding conductor selected for the circuit, feeder, raceway, or equipment connection.
Entered required area	The kcmil area required by the reviewed source record. This value is entered directly; it is not calculated from circuit ampacity, overcurrent protective device rating, or conductor adjustment factors.
Source reference	The record identifying where the entered requirement came from, such as a table record, project note, design calculation, or review reference.

Conductor area is expressed in kcmil, or thousand circular mils. For a grounding conductor comparison, the selected conductor area must be evaluated against the required area using the same area unit and the same reviewed design basis.

A positive area margin shows that the selected conductor area exceeds the entered required area. A zero margin shows that the selected area equals the entered requirement. A negative result identifies a selected area below the entered requirement and requires review before the conductor is accepted for installation.

Calculation Method

The worksheet applies direct arithmetic to the two entered area values:

\(\displaystyle \text{area margin} = \text{selected area} - \text{entered required area}\)

\(\displaystyle \text{area margin percent} = \frac{\text{area margin}}{\text{entered required area}} \times 100\)

It also evaluates whether a Source reference has been entered:

\(\displaystyle \text{source note} = \text{source reference is present}\)

The worksheet reports the values as:

• Selected area
• Entered required area
• Area margin in kcmil
• Area margin as a percentage
• Source note
• Record comparison

The percentage result expresses the excess or deficiency relative to the entered required area. It is not an ampacity margin, fault-current withstand calculation, voltage-drop result, raceway-fill calculation, or conductor temperature correction.

Calculation Example

For the values shown in the worksheet:

Item	Value
Selected conductor area	26.24 kcmil
Entered required area	16.51 kcmil
Source reference	egc-table-record

\(\displaystyle \text{Area margin} = 26.24 - 16.51 = \text{9.73 kcmil}\)

\(\displaystyle \text{Area margin percent} = \frac{9.73}{16.51} \times 100 = \text{58.934\%}\)

The reported result is:

• Selected area: 26.24 kcmil
• Entered required area: 16.51 kcmil
• Area margin: 9.73 kcmil
• Area margin: 58.934%
• Source note: Source recorded
• Record comparison: Entered values comparable

The selected conductor has 9.73 kcmil more area than the entered required area. The worksheet records the comparison, while the source reference preserves the basis used to establish the requirement.

Grounding-Conductor Review Limits

Equipment grounding conductor sizing can depend on installation and design conditions that are outside this worksheet’s arithmetic. The reviewed source must address the applicable electrical condition before its required area is entered.

Field and design review may involve:

• The applicable branch-circuit or feeder overcurrent protection basis
• Raceway type and equipment grounding path
• Whether the conductor is copper, aluminum, or another permitted material
• Any design requirement for increased conductor area
• Parallel conductor arrangements and corresponding grounding provisions
• Available fault current, fault-clearing performance, and engineered grounding requirements
• Equipment listing instructions, project specifications, and AHJ requirements
• Coordination with ungrounded conductor sizing, ampacity, terminal rating, insulation temperature rating, correction factor, adjustment factor, voltage drop, and raceway fill

The Selected conductor area and Entered required area should represent comparable values. Do not compare a conductor area from one material, circuit arrangement, or design condition against a requirement derived for another condition unless the reviewed source specifically supports that comparison.

This worksheet performs arithmetic only; no equipment grounding conductor size is derived from a standards table. The final conductor selection remains subject to the applicable code requirements, project documents, manufacturer instructions, engineered design, and AHJ approval.