Enter the cable diameter, number of strands, and strand diameter into the calculator to determine the missing variable.

Cable Strand Size Calculator

Enter any 2 values to calculate the missing variable




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Cable Strand Size Formula

The following idealized formula can be used to estimate the missing variable for a given cable diameter, number of strands, or strand diameter. This treats the cable diameter as an equivalent bundle diameter based on total cross-sectional area (it ignores insulation and strand packing/lay gaps, so real cables can be slightly larger).

D \approx d\sqrt{N}

Variables:

  • D is the (approximate) cable/bundle diameter
  • N is the number of strands
  • d is the strand diameter

To calculate the cable diameter, multiply the strand diameter by the square root of the number of strands: D ≈ d × √N. To find the number of strands, square the ratio of cable diameter to strand diameter: N ≈ (D ÷ d)² (note: N should be a whole number in real cables; a non-integer result usually means the inputs describe an idealized/approximate condition). To find the strand diameter, divide the cable diameter by the square root of the number of strands: d ≈ D ÷ √N.

What is a Cable Strand?

A cable strand is a single wire or filament that is part of a larger cable. Cables are often made up of multiple strands twisted or braided together to form a stronger, more flexible, and more durable conductor. The size and number of strands in a cable can affect its electrical and mechanical properties, such as resistance, current-carrying capacity, and flexibility. Cable strands are commonly used in electrical wiring, telecommunications, and other applications where reliable and efficient transmission of electrical signals or power is required.

How to Calculate Cable Strand Size?

The following steps outline how to calculate the Cable Strand Size.

  1. First, determine the cable diameter (D).
  2. Next, determine the number of strands (N).
  3. Next, determine the strand diameter (d).
  4. Finally, calculate the missing variable using the appropriate rearrangement of D ≈ d × √N.
  5. After inserting the values and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

Cable diameter (D) = 10 mm

Number of strands (N) = 25

Strand diameter (d) = 2 mm