Does this provide AS/NZS derating factors?

No. The factor values are entered by the user from a project, standard, manufacturer or reviewed source record.

Does this choose a cable size?

No. It compares entered design current with calculated derated capacity only.

Yes. A factor of 1 means the user is not applying a reduction for that item.

Why show utilisation percent?

It helps show how close the entered design current is to the calculated derated capacity.

Does this prove compliance?

No. Standards tables, installation method, cable selection and competent review remain outside this worksheet.

Cable derating worksheet calculator

Iderated = Ibase x Ft x Fg x Fi; utilisation_% = Idesign / Iderated x 100; margin = Iderated - Idesign

Base capacity is entered by the user.
Temperature, grouping and installation factors are entered by the user.
Factors must be above 0 and no more than 1.
The calculator does not reproduce AS/NZS tables or select a final cable size.

Formula variables
Variable	Meaning	Unit	Use
Ibase	Base capacity	A	Entered current capacity before factor application.
Ft	Temperature factor	factor	User-entered temperature factor.
Fg	Grouping factor	factor	User-entered grouping factor.
Fi	Installation factor	factor	User-entered installation or method factor.
Iderated	Derated capacity	A	Base capacity multiplied by all entered factors.
Idesign	Design current	A	Entered current to compare with derated capacity.
utilisation_%	Utilisation percent	%	Design current divided by derated capacity.
margin	Capacity margin	A	Derated capacity minus design current.

Cable derating worksheet calculator technical guide

Apply Australian cable derating worksheet factors entered by the user to a candidate current-capacity record.

Use this calculator when a base cable current-capacity value and a set of source-backed derating factors are already known. It applies the factor chain, then compares the resulting derated capacity with entered design current.

Field use cases

Derating worksheet use cases
Work setting	Real question	Useful action from this page
Cable candidate review	What capacity remains after entered factors?	Multiply base capacity by the factor chain.
Grouped cables	How much does grouping reduce the candidate record?	Keep grouping factor visible in the worksheet.
Hot environment note	How does the entered temperature factor affect margin?	Compare derated capacity with design current.
Design review	Is utilisation high enough to review the assumptions?	Use utilisation percent and margin outputs.
Source traceability	Which factor needs a clearer source?	Export the factor chain beside the result.

This page is not a table lookup. It assumes the reviewer has already selected the factor values from an appropriate source.

Data checklist

Derating input sources
Value	Where it normally comes from	Stop if
Base capacity	Project cable schedule, standard table source or manufacturer data	The source basis is not recorded.
Temperature factor	Project or standards source record	The ambient condition is only guessed.
Grouping factor	Project or standards source record	The cable grouping does not match the factor basis.
Installation factor	Project, manufacturer or engineering source	The installation method is unresolved.
Design current	Load calculation or circuit design record	The current basis differs from the cable schedule.

The calculator keeps every factor visible because factor selection is the sensitive part of this workflow.

Method comparison matrix

Derating method boundary
Method element	What this calculator does	What remains outside
Factor chain	Multiplies temperature, grouping and installation factors.	Selecting the correct factor values.
Derated capacity	Multiplies base capacity by the combined factor.	Establishing the base capacity table value.
Utilisation	Compares design current with derated capacity.	Deciding whether the candidate cable is suitable.
Review flags	Highlights high utilisation or negative margin.	Final project and standards review.

The worksheet is useful when it exposes assumptions. It should not hide factor selection behind an automatic answer.

Worked records

Derating examples
Situation	Inputs	Result	Record use
Grouped cable record	160 A base, 118 A design, 0.91 x 0.82 x 0.95	113.42 A derated capacity	Review factor chain and candidate record.
Moderate screen	125 A base, 82 A design, mild reductions	Capacity remains above design current	Keep source factors with the record.
Low factor review	200 A base, 120 A design, low combined factor	Low combined factor review applies	Recheck source values and project assumptions.

These examples are not table values. They show how the arithmetic behaves once the user supplies the source values.

Stop points

Factor values have no documented source.
Base capacity is copied from the wrong cable, installation or temperature basis.
Design current is above derated capacity and no candidate review has been done.
The result is being treated as cable selection or compliance approval.
Voltage drop, protection, fault rating and installation method are not checked.

A useful export record includes base capacity, design current, every factor, combined factor, derated capacity, utilisation, margin and reviewer.

Derating reference: DERATE-RUN-1
Base capacity: 160 A
Design current: 118 A
Factors: 0.91 x 0.82 x 0.95

Combined factor0.709 from the entered factor chain.
Derated capacity113.42 A from base capacity and combined factor.
Utilisation104.04% of the derated capacity.

Derated capacity113.42 A

Capacity margin is -4.58 A.

The entered factor chain leaves derated capacity below the design current, so the source data and candidate record need review.

Base capacity and factors are entered by the user.
No controlled current-carrying-capacity table is embedded.
The output is a worksheet comparison, not a final cable selection.

Derating reference: DERATE-OK-1
Base capacity: 125 A
Design current: 82 A
Factors: 0.96 x 0.9 x 1

Combined factor0.864 from the entered factor chain.
Derated capacity108 A from base capacity and combined factor.
Utilisation75.93% of the derated capacity.

Derated capacity108 A

Capacity margin is 26 A.

The derated capacity remains above design current on this worksheet, with the factor basis kept visible.

Factor values are entered from a project source.
The installation factor can be 1 when no reduction is being applied by the user.
Voltage drop and protection checks remain separate.

Derating reference: DERATE-LOW-FACTOR
Base capacity: 200 A
Design current: 120 A
Factors: 0.82 x 0.75 x 0.9

Combined factor0.554 from the entered factor chain.
Derated capacity110.7 A from base capacity and combined factor.
Utilisation108.4% of the derated capacity.

Derated capacity110.7 A

Capacity margin is -9.3 A.

The low combined factor should prompt review of source values and the wider cable-selection record.

The factor chain is deliberately visible.
The result does not choose a larger cable.
Australian project requirements and competent review remain controlling.