Guy Wire Tension Calculator

Plan secure guying with clear load inputs. See tension, utilization, and stretch in seconds easily. Download neat reports for site checks and approvals fast.

Calculated output
Design tension and checks
Inputs
Loads, geometry, and strength options
Units: kN, m, mm, degrees

Example: wind or conductor transverse load.
Optional: uplift or vertical component.
Load is divided equally for quick checks.
Angle input method
Angle is clamped between 5° and 85°.
Typical range: 30°–60°.
Measured to the guy connection point.
Horizontal offset to anchor point.
Used to derive required breaking strength.
Accounts for grips, clamps, and hardware.
If provided, a PASS/FAIL check is shown.
Used only when strength is entered.
Optional stretch estimate
Uses a straight, elastic approximation: δ = (T × L) / (A × E).
Typical steel ≈ 200 GPa.
Area is computed as π d² / 4.
Enter known metallic area if available.
Stretch is reported in millimetres, using service tension.
Reset
Example
Sample inputs and expected outputs
H total (kN) V total (kN) Guys Angle (deg) SF Req. tension / guy (kN) Req. MBS (kN)
12.00 2.00 2 45 2.50 8.49 23.58
20.00 0.00 3 40 3.00 8.70 28.99
8.00 3.00 1 60 2.00 6.00 13.33
Example outputs assume termination efficiency of 0.90 and no pretension.
Formula used
Core relationships
Load sharing (quick check)
Per-guy loads are assumed equal:
Hg = H / nVg = V / n
Tension from fixed angle
With guy angle α from ground:
TH = Hg / cos(α)
TV = Vg / sin(α)
Design tension is conservative:
T = max(TH, TV)
Strength requirement
Required minimum breaking strength (MBS):
MBSreq = (T × SF) / η
where η is termination efficiency.
Elastic stretch (optional)
Linear elastic approximation:
δ = (T × L) / (A × E)
Reported as mm using service tension.
Notes: This tool is intended for preliminary sizing and documentation. Real projects may require additional load cases, unequal guy sharing, dynamic effects, and code-specific factors.
How to use
Practical workflow
  1. Enter total horizontal and vertical loads in kN.
  2. Set the number of guy wires that share the load.
  3. Choose angle input: enter α, or provide height and distance.
  4. Set safety factor and termination efficiency for hardware losses.
  5. Optionally enter breaking strength to get a PASS/FAIL check.
  6. Add length and wire size to estimate elastic stretch.
  7. Click Calculate, then export CSV or PDF for records.
Article
Guy wire tension: practical sizing notes for construction work

Guy wires stabilize slender poles, masts, and temporary towers by converting lateral loads into axial tension. A dependable tension estimate helps you select wire size, hardware, and anchor capacity with fewer site revisions. In practice, the dominant load is often horizontal (wind, conductor pull, or equipment offset), while vertical effects come from uplift, slope, or attachment geometry. Because the guy angle is fixed by site constraints, tension rises rapidly as the angle gets flatter. A 30° guy typically carries much higher tension than a 60° guy for the same horizontal demand.

This calculator uses a conservative component approach. Total horizontal and vertical loads are divided by the number of guys assumed to share the demand. The selected angle then converts those component demands into tension requirements. Hardware losses are considered with a termination efficiency factor, and a safety factor converts working tension into required minimum breaking strength. If you enter a known breaking strength, the tool reports utilization and a clear pass/fail check. For quick field documentation, the CSV and PDF exports capture the inputs, the required tension, and the strength requirement in a clean format.

When applying results, confirm that load sharing is realistic. Unequal guys, imperfect alignment, and installation tolerances can shift demand to one wire. Anchor type and soil conditions also matter: even if wire strength is adequate, anchors must resist both the axial tension and any vertical component without excessive movement. For long spans or high pretension, consider stretch. This tool provides an elastic stretch estimate using wire length, area, and modulus. Real ropes may exhibit additional constructional stretch and seating, so treat the value as a baseline.

Example dataset: H = 12 kN, V = 2 kN, two guys at 45°, safety factor 2.5, efficiency 0.90. The calculator returns about 8.49 kN required tension per guy and about 23.58 kN required breaking strength. Use these outputs to select wire and fittings, then verify against your project specification and inspection plan.

FAQ
Common questions
1) What does “required tension” mean?
It is the conservative per‑guy tension needed to provide the required horizontal and vertical components at the selected angle, before strength selection and detailed design checks.
2) Why does a smaller angle increase tension?
At flatter angles, the same horizontal load must be carried with a smaller horizontal component of tension, so the total tension increases quickly as cos(α) decreases.
3) What is termination efficiency?
It represents strength loss from grips, clamps, thimbles, and fittings. Use manufacturer data when available; otherwise use a reasonable preliminary value such as 0.85–0.95.
4) How is required breaking strength calculated?
The tool uses MBSreq = (T × SF) / η. Safety factor and efficiency convert working tension into a minimum breaking strength target for selecting wire and hardware.
5) Does the stretch value represent real rope behavior?
It is an elastic estimate only. Wire ropes can show seating and constructional stretch, plus temperature effects. Treat the number as a baseline, not a final installation prediction.
6) What if I only know horizontal load?
Set vertical load to zero. The calculator will use T ≈ Hg/cos(α). Then verify anchor capacity, pole reactions, and any project‑specific load combinations.
7) Can I rely on equal load sharing?
Equal sharing is a quick check. For final work, consider alignment, installation tolerances, unequal angles, and stiffness differences that can shift more load to a single guy.

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