Construction / CALCULATOR

Parabolic Cable Sag Approximation

Parabolic Cable Sag Approximation with explicit measurements, assumptions and a worked example.

Runs on your deviceUpdates as you typeFormula & example ↓
01

Your inputs

Adjust the values to explore a different result.

N/m
Enter uniform load per horizontal length in N/m.
m
Enter horizontal span in m.
N
Enter horizontal tension component in N.

Formula

midspan sag=wL²/(8H).
  • Use the units shown beside each field.
  • Results update automatically whenever you change an input.
  • Displayed values use up to four decimal places, or scientific notation for very small or large numbers. Calculations use standard floating-point arithmetic; exact integer and fraction tools identify their own precision rules.
  • Equal-height supports and shallow parabolic cable under uniform horizontal load; not an exact self-weight catenary or a cable safety check.

Example Calculation

Example inputs
  • Uniform load per horizontal length: 100 N/m
  • Horizontal span: 20 m
  • Horizontal tension component: 10000 N

Uniform load per horizontal length = 100 N/m; Horizontal span = 20 m; Horizontal tension component = 10000 N. Primary result: 0.5.

Frequently asked questions

How do I use this calculator?

Enter uniform load per horizontal length, horizontal span, horizontal tension component. The result updates automatically. Use Reset to restore the example values.

What method does it use?

midspan sag=wL²/(8H).. Equal-height supports and shallow parabolic cable under uniform horizontal load; not an exact self-weight catenary or a cable safety check.

Why might a rounded result differ?

The calculation keeps full numeric precision internally, then rounds the displayed result. Rounding intermediate steps by hand can produce a slightly different answer.

Are my inputs saved online?

No. This calculator processes your inputs in your browser. A recently used list stores only calculator names on this device, not your entered values.

Check the assumptions and units before using this result. Read about calculation methods.