Check every consecutive axle group
Federal Bridge Formula Calculator
Apply the Federal Bridge Gross Weight Formula to one consecutive axle group. The result shows the raw formula, a conservative 500 lb table increment, the federal gross ceiling, and the margin against the actual group weight.
- Time
- Takes about 1 minute
- Privacy
- Runs in your browser
- Output
- Bridge Formula
Your inputs
Enter the load details
Planning result
2,280 lb under the calculated limit
For 5 consecutive axles over 51 ft, the formula returns 80,000 lb.
- Formula result
- 80,000 lb
- Actual group weight
- 77,720 lb
- Margin
- 2,280 lb
What this means
- 500 × [(51 × 5) ÷ (5 − 1) + 12 × 5 + 36] = 79,875 lb.
- Federal bridge-formula tables express the result to the nearest 500 lb.
Assumptions
- Axles are consecutive and length is measured between the extreme axles in the group.
- The entered weight is the combined weight carried by that same axle group.
- This is a federal planning check, not a complete legal verdict. Also check single/tandem axle, gross, state, tire and equipment limits.
Worked example
See the calculation in plain English.
Five axles over 51 ft produce 79,875 lb before table handling, which is 80,000 lb to the nearest 500 lb and remains at the federal gross ceiling.
What this tool does not decide
- A complete check applies the formula to every consecutive group, not only the full vehicle.
- State, grandfather, single/tandem, tire and equipment rules may bind first.
Common questions
Use the result without guessing.
What do L and N mean in the Bridge Formula?
L is the distance in feet between the extreme axles of the group. N is the number of consecutive axles within those extremes.
Does a five-axle truck have only one bridge check?
No. The formula can apply to every qualifying consecutive subset. A five-axle vehicle has multiple groups that need to be evaluated.