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Cable Derating Factor Calculator

Combine separate ambient, grouping, installation and thermal factors before applying them to a verified reference cable capacity.

Inputs

Project inputs and assumptions

Range: 0.01–100,000 A

Enter a verified reference ampacity before installation corrections.

Range: 0.01–2

Enter the verified factor for the actual ambient or surrounding condition from the applicable current table or manufacturer data.

Range: 0.01–2

Enter the verified factor for adjacent loaded circuits or cables. Count only the loaded circuits and arrangement covered by the source table.

Range: 0.01–2

Enter the verified factor for the actual installation method and cable arrangement. Do not use a generic value when the source data distinguishes methods.

Range: 0.01–2

Enter an additional verified thermal correction that is not already represented by the other factors. Use 1.0 only when the source basis confirms that no additional factor applies.

Range: 0–100,000 A

Enter the assessed design current Ib in amperes after the applicable load and diversity assessment.

Result

Adjusted cable capacity (A)
32.15
Capacity margin (A)
0.15
Combined correction factor
0.6430
Smallest entered correction factor
0.8000
Capacity check
The adjusted capacity meets the entered design current. Confirm cable selection, voltage drop, fault withstand, terminations and applicable requirements separately.

Formula

Calculation logic

Formula definitions and substituted values.

Before relying on the result

  • Combine known correction factors for a proposed route
  • Show adjusted capacity and limiting margin before cable selection
  • Enter factors from the applicable current table, manufacturer data or engineering basis; this tool does not infer the factors from a wiring method.

Related calculators

Enter factors from the applicable current table, manufacturer data or engineering basis; this tool does not infer the factors from a wiring method.