Calculate auger length, eave height, or bin diameter for a bin from two known values in inches, feet, centimeters, or meters with unit conversion.
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Auger Length Formula
The auger length calculation treats the bin height and half of the bin diameter as the two legs of a right triangle. The auger is the sloped side, or hypotenuse.
- AL = auger length
- E = eave height of the bin
- D = bin diameter
- D/2 = bin radius, or the horizontal distance from the bin edge to the center
If you need to solve for a different missing value, the same right-triangle relationship can be rearranged.
- To calculate auger length: enter the eave height and bin diameter. The calculator finds the sloped auger length needed to reach the center of the bin.
- To calculate eave height: enter the auger length and bin diameter. The calculator finds the vertical height that can be reached.
- To calculate bin diameter: enter the auger length and eave height. The calculator finds the bin diameter that matches those dimensions.
Common Auger Lengths for Bin Sizes
The table below shows approximate auger lengths for common bin dimensions. These values assume the auger reaches from ground level to the center of the bin at the eave height.
| Eave Height | Bin Diameter | Bin Radius | Approx. Auger Length |
|---|---|---|---|
| 18 ft | 18 ft | 9 ft | 20.12 ft |
| 20 ft | 24 ft | 12 ft | 23.32 ft |
| 24 ft | 30 ft | 15 ft | 28.30 ft |
| 28 ft | 36 ft | 18 ft | 33.29 ft |
| 32 ft | 42 ft | 21 ft | 38.29 ft |
Length Unit Conversions
| Unit | Equivalent in Feet | Example |
|---|---|---|
| Inches | 1 in = 0.083333 ft | 120 in = 10 ft |
| Feet | 1 ft = 1 ft | 25 ft = 25 ft |
| Centimeters | 1 cm = 0.0328084 ft | 300 cm = 9.8425 ft |
| Meters | 1 m = 3.28084 ft | 8 m = 26.2467 ft |
Example Problems
Example 1: Calculate auger length
You have a bin with an eave height of 24 ft and a diameter of 30 ft.
The required auger length is about 28.30 ft.
Example 2: Calculate eave height
You have a 35 ft auger and a bin diameter of 40 ft.
The eave height that matches those values is about 28.72 ft.
FAQ
Why does the formula use half of the bin diameter?
The auger usually needs to reach the center of the bin. The horizontal distance from the side of the bin to the center is the radius, which is half of the diameter. That radius and the eave height form the two legs of the right triangle.
Should you round the calculated auger length up?
Yes, in most practical cases you should round up to the next available auger size. The formula gives the straight-line geometric length. It does not account for ground clearance, discharge spout position, setup angle limits, uneven ground, or extra reach needed for safe placement.
Why does the calculator reject some values?
Some combinations are not physically possible. For example, if you enter an auger length that is shorter than the eave height, the auger cannot reach that height. If you solve for eave height, the auger length must also be at least half of the bin diameter.
