Axle weight limits in Canada and the United States
Updated October 18, 2026
A truck can be under its gross weight limit and still be overweight: every axle group has its own limit. This guide sums up the rules for a tractor pulling a 53-foot semi-trailer.
Three limits at the same time
- The axle or axle-group limit: steer, drive tandem, trailer tandem or tridem.
- The gross weight of the combination, which depends on the number of axles.
- Tire and axle ratings set by the manufacturer. They apply even when the law allows more.
In the United States, the Bridge Formula also limits weight according to axle spacing.
Canada: the interprovincial weights and dimensions agreement
The provinces share a common agreement for interprovincial trucking (the CCMTA Memorandum of Understanding). It sets minimum limits that every province accepts on its main highways. For a tractor semi-trailer:
| Axle group | Limit |
|---|---|
| Steer axle | 5,500 kg (12,125 lb) |
| Single axle (dual tires) | 9,100 kg (20,062 lb) |
| Tandem (drive or trailer) | 17,000 kg (37,479 lb) |
| Tridem, 2.4–3.0 m spread | 21,000 kg (46,297 lb) |
| Tridem, 3.0–3.6 m spread | 23,000 kg (50,706 lb) |
| Tridem, 3.6–3.7 m spread | 24,000 kg (52,911 lb) |
| Gross, 5 axles (tandem/tandem) | 39,500 kg (87,083 lb) |
| Gross, 6 axles (tandem/tridem) | 46,500 kg (102,515 lb) |
Each province may allow more on its own network, and less on some roads or during spring thaw.
Quebec
Limits are set by Quebec’s regulation on load and size limits for road vehicles. They depend on axle type, spacing and tires, and the Ministry of Transportation publishes a detailed guide. In spring, allowed loads drop during the thaw period.
AxleLoad 53 uses 5,500 kg on the steer axle, 17,000 kg per tandem, 24,000 kg for a tridem and 41,500 kg (5 axles) or 46,500 kg (6 axles) gross by default. These are reference values: check the ones that apply to your exact configuration.
Ontario
Ontario applies its own configuration rules (Regulation 413/05, known as “SPIF”, for newer vehicles). Limits depend on configuration and spacing: check with the Ontario Ministry of Transportation before a first trip.
United States: federal Interstate rules
| Item | Federal limit |
|---|---|
| Single axle | 20,000 lb |
| Tandem | 34,000 lb |
| Gross weight | 80,000 lb |
| Axle groups | Bridge Formula B |
Federal law sets no separate steer axle limit: it is limited by tire and axle ratings, and several states cap it by tire width. AxleLoad 53 uses 12,000 lb as a reference value, which matches most highway tractors.
The Bridge Formula
It protects bridges by spreading weight over enough distance. For any group of consecutive axles:
W = 500 × ( L×N ÷ (N−1) + 12×N + 36 )
- W: maximum weight on the group, in pounds, rounded to the nearest 500 lb;
- L: distance in feet between the first and last axle of the group;
- N: number of axles in the group.
Example: with 5 axles, you need at least 51 feet between the steer axle and the last trailer axle to reach 80,000 lb. At 50 feet, it gives about 79,250 lb. Exception: two consecutive tandems at least 36 feet apart may carry 68,000 lb together.
How to stay legal
- Plan the load before loading, using the real weight of each pallet.
- Weigh the combination on a certified scale, axle group by axle group.
- Correct with the trailer slider, the fifth wheel or by moving pallets. The guide Balancing a 53-foot trailer explains what each adjustment does.
- Keep a margin: one mis-declared pallet or a fuel stop is enough to go over.
More guides
This guide is for information only. Legal limits change and depend on the road, the season and your permits: always check with the competent authority. Certified scale weights govern.