CCS conductivity should be read with its units, reference temperature and measurement method. A grade label alone is not a complete electrical specification.
Read % IACS correctly
IACS means International Annealed Copper Standard. The reference conductivity is 100% IACS, corresponding to 58 MS/m at 20°C. The number 58 is a value in MS/m; it is not 58% IACS.
A CCS designation of 40% IACS expresses conductivity relative to that reference. It does not mean that the wire contains 40% copper, or that its copper layer occupies 40% of the diameter.
Request comparable data
For an electrical comparison, request the conductor dimensions, measured resistance or resistivity, test method and reference temperature. For a stranded conductor, identify the strand construction and the test specimen.
Specify the frequency and required performance separately for signal applications. Do not infer high-frequency performance or allowable current from a DC conductivity grade alone.
Make the application decision
Review conductivity alongside mechanical properties, connections, insulation and operating conditions. Confirm the test evidence for the proposed material before specifying it as a replacement.
Discuss a conductivity requirement: send the construction and electrical data your project needs.