SAG Calculator
Calculate sag (sagitta) for cables, wires, ropes, chains, and geometric applications
Calculate SAG
Calculation Type
Measurement Units
Geometric Parameters
Geometric sag (sagitta) is the perpendicular distance from the midpoint of a chord to the arc
SAG Calculation Results
Formula Used:
Geometric Sag = R - √(R² - (D/2)²)
Where R = 0.000 ft, D = 0.000 ft
Sag = 0.000 - √(0.000² - (0.000/2)²) = 0.0000 ft
Application Guidelines
Example Calculations
Geometric Sag Example
Problem: Find sag of an arch with 10m radius and 13m chord
Formula: Sag = R - √(R² - (D/2)²)
Calculation: Sag = 10 - √(10² - (13/2)²) = 10 - √(100 - 42.25) = 10 - 7.6 = 2.4m
Cable Sag Example
Problem: 100ft power line span, 0.5 lbs/ft weight, 1000 lbs tension
Formula: Sag = (w × L²) / (8 × T)
Calculation: Sag = (0.5 × 100²) / (8 × 1000) = 5000 / 8000 = 0.625 ft = 7.5 inches
Common Material Weights
Sag Guidelines
Power lines: 2-5% of span length
Suspension bridges: 8-12% of span
Antenna guy wires: 1-3% of span
Geometric arches: Varies by design
Consider wind and ice loads
Temperature affects cable sag
Understanding Sag Calculations
What is Sag?
Sag refers to the vertical displacement or droop in a cable, wire, rope, or geometric curve. It's a critical parameter in engineering design, affecting both structural integrity and aesthetic appeal.
Types of Sag
- Geometric Sag (Sagitta): Distance from chord midpoint to arc
- Cable Sag: Vertical drop in suspended cables under load
- Uniform Load Sag: Distributed weight along entire span
- Point Load Sag: Concentrated load at specific location
Key Formulas
Geometric: Sag = R - √(R² - (D/2)²)
Uniform Load: Sag = (w × L²) / (8 × T)
Point Load: Sag = (P × a × b) / (T × L)
Common Applications
- • Power transmission lines
- • Suspension bridge cables
- • Architectural arches and domes
- • Antenna guy wires
- • Construction cable installations