Federal Bridge Formula establishes the maximum weight any set of axles may legally carry on the Interstate roadways. The FBF is a mathematical formula used to determine the appropriate weight of loads based on axle configuration (number of axles, axle spacing, weight distribution). The formula is as follows:

- W = the maximum weight in pounds that can be carried on a group of two or more axles to the nearest 500 pounds (230 kg).
- L = spacing in feet between the outer axles of any two or more consecutive axles.
- N = number of axles being considered.

This formula can look intimidating, because of that, Oversize.io has developed a calculator to determine whether your load meets FBF guidelines. (See Also: State Axle Weight Regulations)

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### Federal Bridge Formula Calculator

### Vehicle configuration