Axle Load & Bridge Formula Calculator
Check per-axle legal weights and Federal Bridge Formula compliance for your vehicle configuration across 51 US jurisdictions and 13 Canadian provinces and territories — the same regulatory reference behind our permit requirements pages.
Vehicle Configuration
Axle Layout
Axle Configuration Details
| Axle | Spacing to previous (ft) | Tire type (reference only) | Tire width (in) (reference only) | Weight (lbs) | |
|---|---|---|---|---|---|
| #1 | — | ||||
| #2 | |||||
| #3 | |||||
| #4 | |||||
| #5 |
Simplified model: tire type and tire width are recorded for your reference only and do not affect the calculated verdicts. Jurisdiction rules that scale limits by tire configuration or axle-spread brackets (e.g. Québec and Ontario tables, spring-thaw reductions) are not yet modelled — results for those jurisdictions are provisional.
Select Jurisdictions for Analysis0 of 64 selected
United States
Canada
indicates jurisdictions where state/province-specific limits have not yet been verified — federal/baseline formulas are applied and flagged in the results.
Bridge Formula Information
US Federal Bridge Formula (23 CFR 658.17)
W = 500 × (LN/(N−1) + 12N + 36), where W is the maximum weight in pounds (rounded to the nearest 500 lb) that any group of two or more consecutive axles may carry, L is the distance in feet between the outer axles of the group, and N is the number of axles in the group. Exceptions: a single axle may carry 20,000 lb and a tandem (two axles spaced 96 inches or less apart) may carry 34,000 lb. Gross vehicle weight is capped at 80,000 lb on the Interstate system.
W = 500 × ( LN / (N − 1) + 12N + 36 )
Canadian provinces — axle-group weight tables
Canadian provinces do not use a US-style inter-axle bridge formula. Weights are governed by axle-group and gross-weight tables under the federal-provincial Memorandum of Understanding on Interprovincial Weights and Dimensions and each province's own regulation. Québec, for example, sets limits in the Regulation respecting the norms of loads and sizes (C-24.2, r. 31), with spread-dependent group limits and spring-thaw (période de dégel) reductions; Ontario uses SPIF configuration tables under O. Reg. 413/05.
See per-jurisdiction permit requirements, fees and portals on our Permit Requirements pages.
Need Professional Weight Analysis?
Route-specific bridge restrictions, permit strategy, escort planning and jurisdiction-verified weight rulings — our engineering team turns this planning estimate into a defensible determination.