Length of Cable with Sag

The Cable Length calculator estimates the length of cable needed between a span with a sag.

INSTRUCTIONS: Choose units and enter the following:

• (L) Length of Span
• (h) Height of Sag

Cable Length (CL): The length is returned in feet.  However, this can be automatically converted to compatible units via the pull-down menu.

The Math / Science

Since the gravitational force on a cable creates a parabolic shape, the formula for the length of cable can be approximated as

CL = L + 8 h² / (3 ⋅L)

where

• CL = Length of cable in the span
• h = height of the sag 
• L = length of span

Cable Calculators

• Length of Cable with Sag
• Cable Anchor Force
• Mid-span Cable Tension