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Axle Weight Calculator — Federal Bridge Formula
Check legal axle weight limits using the federal bridge formula. Select your axle configuration and state to see if your load is compliant — and if an overweight permit is required.
Federal Legal Weight Limits by Axle Configuration
Single Axle
20,000
lbs legal max
Tandem Axle
34,000
lbs legal max
Tridem Axle
42,000
lbs legal max
Quad Axle
50,000
lbs legal max
5-Axle Semi
80,000
lbs legal max
6-Axle
80,000
lbs legal max
7-Axle Lowboy
105,500
lbs legal max
9-Axle Multi
129,000
lbs legal max
Federal limits. Some states allow higher weights with permits. Verify with state DOT before dispatch.
The Federal Bridge Formula
State Weight Limits — Key States
| State | GVW Limit | Single Axle | Tandem Axle | Notes |
|---|---|---|---|---|
| TX | 80,000 lbs | 25,000 lbs | 46,000 lbs | TX allows 25k single axle on state highways with permit |
| CA | 80,000 lbs | 20,000 lbs | 34,000 lbs | Strict enforcement. No tolerance for bridge formula. |
| FL | 80,000 lbs | 22,000 lbs | 44,000 lbs | FL allows 22k single and 44k tandem on state roads |
| OH | 80,000 lbs | 20,000 lbs | 34,000 lbs | OH has strict seasonal weight limits (spring thaw) |
| WA | 105,500 lbs | 20,000 lbs | 34,000 lbs | WA allows up to 105,500 lbs GVW on some routes |
| MI | 164,000 lbs | 18,000 lbs | 32,000 lbs | MI has highest GVW limits in US on qualified routes |
| NY | 80,000 lbs | 22,400 lbs | 36,000 lbs | NY has NYSDOT bridge formula separate from federal |
| PA | 80,000 lbs | 20,000 lbs | 34,000 lbs | PA has 6% enforcement tolerance on certified scales |
| AZ | 80,000 lbs | 20,000 lbs | 34,000 lbs | AZ enforces bridge formula strictly on I-10, I-40 |
| LA | 88,000 lbs | 20,000 lbs | 34,000 lbs | LA allows 88k GVW on National Highway System |
Reference data verified Q1 2026. Confidence: partially_verified. Always confirm with state DOT before dispatch.
Axle Weight FAQs
What is the federal bridge formula?+
The federal bridge formula limits the weight any set of axles can carry based on the spacing between them. W = 500 × (LN ÷ (N−1) + 12N + 36). Where W = max weight (lbs), L = distance between outer axles (ft), N = number of axles. It protects bridges from overloading.
What is the maximum legal weight for a 5-axle semi?+
The federal cap is 80,000 lbs gross. Single axle: 20,000 lbs. Tandem axle: 34,000 lbs. Many states match federal limits. Michigan and Washington allow higher weights on specific routes with permits.
What happens if I exceed axle weight limits?+
Overweight loads require permits in every state you travel through. Without a permit, you risk fines of $100"“$5,000+ per violation, load rejection at weigh stations, and potential bridge damage liability.
Do pilot cars have their own weight requirements?+
Pilot cars and escort vehicles must comply with standard highway vehicle weight limits. They are not exempt from axle weight regulations and must have valid registration.