Select sling angle, vertical height or leg length, then enter the two displayed values. Angle is measured from horizontal; each length can use its own unit.
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Sling Angle Formula
The sling angle calculator uses right-triangle trigonometry. The sling length is the hypotenuse, the sling height is the vertical side, and the sling angle is measured from the horizontal.
- H = sling height
- L = sling length
- SA = sling angle
- sin = sine function
- arcsin = inverse sine function
If you enter sling length and sling angle, the calculator finds sling height with H = L * sin(SA).
If you enter sling height and sling angle, the calculator finds sling length with L = H / sin(SA).
If you enter sling height and sling length, the calculator finds sling angle with SA = arcsin(H / L).
The length and height values are converted to meters internally. The angle is converted to radians internally, then converted back to your selected unit.
Common Sling Angle Ratios
These values show the relationship between sling angle and the height-to-length ratio. The ratio is equal to sin(SA).
| Sling Angle | sin(angle) | Height as % of Sling Length |
|---|---|---|
| 15° | 0.2588 | 25.88% |
| 30° | 0.5000 | 50.00% |
| 45° | 0.7071 | 70.71% |
| 60° | 0.8660 | 86.60% |
| 90° | 1.0000 | 100.00% |
Unit Conversion Reference
| Unit | Conversion to Base Unit |
|---|---|
| 1 centimeter | 0.01 meters |
| 1 foot | 0.3048 meters |
| 1 inch | 0.0254 meters |
| 1 degree | π / 180 radians |
Example Problems
Example 1: Find sling height
You have a sling length of 10 ft and a sling angle of 30°.
The sling height is 5 ft.
Example 2: Find sling angle
You have a sling height of 4 m and a sling length of 8 m.
The sling angle is 30°.
FAQ
What angle range is valid for this sling angle calculation?
The geometry range is 0° to 90°, or 0 to π/2 radians. Sling leg length must be positive. Solving leg length also requires positive height and a nonzero angle. Zero height can produce a mathematical zero angle, but not a usable lifting configuration. This calculator does not determine sling capacity or approve a lift; follow the manufacturer’s ratings and lift plan. Crosby rigging guidance does not recommend horizontal angles below 30°.
Why cannot sling height be greater than sling length?
The sling length is the hypotenuse of the right triangle. The hypotenuse must be the longest side. If the sling height is greater than the sling length, the triangle is not possible, so the sling angle cannot be calculated.
Is the sling angle measured from horizontal or vertical?
This calculator treats the sling angle as measured from the horizontal. That is why the formula uses sin(angle) to connect sling height and sling length. If your angle is measured from vertical, convert it first by subtracting it from 90°.
