Skip to main content
Calcimator

Bridge Formula Calculator

Calculate maximum legal weight by axle spacing using Federal Bridge Formula B.

Inputs

ft
lbs

Results

Bridge Formula Max Weight

79,875 lbs

≈ 7 elephants

Effective Limit

79,875 lbs

≈ 7 elephants

Compliance StatusLegal
Weight per Axle15,000 lbs
Over/Under Limit-4,875 lbs
% of Limit93.9%
Available Capacity4,875 lbs
Min Spacing for Weight44 ft
How to Use This Calculator
  1. Enter the Number of Axles in the axle group being evaluated.
  2. Set the Outer Axle Spacing in feet (distance from first to last axle in the group).
  3. Enter the Actual Weight on the axle group in lbs.
  4. Review the Bridge Formula Max Weight, Compliance Status (legal or over), and Over/Under Limit.
  5. If over the limit, check the Minimum Spacing for Weight to see what axle spread would make the load legal.

How the result changes with Outer Axle Spacing

Outer Axle SpacingBridge Formula Max WeightEffective Limit
9.654,000 lbs54,000 lbs
2463,000 lbs63,000 lbs
4073,000 lbs73,000 lbs
5481,750 lbs80,000 lbs

What each input means

Number of Axles
Number of axles in the group being evaluated.
Outer Axle Spacing
Distance in feet between the first and last axle of the group.
Actual Weight on Group
Actual weight on the axle group being evaluated.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    Number of Axles = 5, Outer Axle Spacing = 51, Actual Weight on Group = 75000 = 3 input(s) provided
  2. Calculate Bridge Formula Max Weight
    Bridge Formula Max Weight
    79875 = 79875
  3. Calculate Effective Limit
    Effective Limit
    79875 = 79875
  4. Calculate Compliance Status
    Legal = Legal
  5. Calculate Weight per Axle
    Weight per Axle
    15000 = 15000

Engine last updated . Checked against 2 independently-derived tests — how we verify calculators.

Related Calculators

The questions that sit next to this one — chosen by subject, including calculators filed under a different category.

Trucking & Commercial

Load Weight Distribution

Calculate axle weights for legal compliance with federal weight limits.

Trucking & Commercial

Freight Rate Calculator

Calculate per-mile rate from fuel, insurance, maintenance, and driver costs.

Prosthodontics

Fixed Bridge Design Calculator

Pontic and retainer design from Ante's law analysis.

Trucking & Commercial

CDL Trip Planner

Plan HOS-compliant driving schedules with rest stops and fuel breaks.

More in Aviation, Marine & Transport.