Federal (Interstate Highway System) Truck Weight Limits
Complete guide to commercial vehicle weight regulations in Federal (Interstate Highway System), including axle limits, permit requirements, and seasonal restrictions.
Weight Limits
| Axle Type | Federal (Interstate Highway System) Limit |
|---|---|
| Single Axle | 20,000 lbs |
| Tandem Axle | 34,000 lbs |
| Gross Vehicle Weight | 80,000 lbs |
| Steer Axle (min) | 12,000 lbs |
| Steer Axle (max) | 20,000 lbs |
Showing interstate route, standard operation.
Bridge Formula
Federal (Interstate Highway System) uses the standard Federal Bridge Formula to calculate maximum weight on groups of consecutive axles.
- W = Maximum weight (lbs)
- L = Distance between outer axles (ft)
- N = Number of axles in the group
Permissible Gross Loads in Federal (Interstate Highway System)
| Permissible Gross Loads for Vehicles in Federal (Interstate Highway System) | ||||||||
|---|---|---|---|---|---|---|---|---|
| Based on FederalBridge Formula: W = 500 × [LN/(N-1) + 12N + 36] | ||||||||
| Showing interstate route, standard operation | ||||||||
Distance (ft) L | 2 AXLES | 3 AXLES | 4 AXLES | 5 AXLES | 6 AXLES | 7 AXLES | 8 AXLES | 9 AXLES |
| 4 | 34,000 | — | — | — | — | — | — | — |
| 5 | 34,000 | — | — | — | — | — | — | — |
| 6 | 34,000 | — | — | — | — | — | — | — |
| 7 | 34,000 | — | — | — | — | — | — | — |
| 8 | 34,000 | 42,000 | — | — | — | — | — | — |
| 9 | 39,000 | 42,500 | — | — | — | — | — | — |
| 10 | 40,000 | 43,500 | — | — | — | — | — | — |
| 11 | 40,000 | 44,000 | — | — | — | — | — | — |
| 12 | 40,000 | 45,000 | 50,000 | — | — | — | — | — |
| 13 | 40,000 | 45,500 | 50,500 | — | — | — | — | — |
| 14 | 40,000 | 46,500 | 51,500 | — | — | — | — | 80,000 |
| 15 | 40,000 | 47,000 | 52,000 | — | — | — | — | 80,000 |
| 16 | 40,000 | 48,000 | 52,500 | 58,000 | — | — | — | 80,000 |
| 17 | 40,000 | 48,500 | 53,500 | 58,500 | — | — | — | 80,000 |
| 18 | 40,000 | 49,500 | 54,000 | 59,000 | — | — | — | 80,000 |
| 19 | 40,000 | 50,000 | 54,500 | 60,000 | — | — | — | 80,000 |
| 20 | 40,000 | 51,000 | 55,500 | 60,500 | 66,000 | — | — | 80,000 |
| 21 | 40,000 | 51,500 | 56,000 | 61,000 | 66,500 | — | — | 80,000 |
| 22 | 40,000 | 52,500 | 56,500 | 61,500 | 67,000 | — | — | 80,000 |
| 23 | 40,000 | 53,000 | 57,500 | 62,500 | 68,000 | — | — | 80,000 |
| 24 | 40,000 | 54,000 | 58,000 | 63,000 | 68,500 | 74,000 | — | 80,000 |
| 25 | 40,000 | 54,500 | 58,500 | 63,500 | 69,000 | 74,500 | 80,000 | 80,000 |
| 26 | 40,000 | 55,500 | 59,500 | 64,000 | 69,500 | 75,000 | 80,000 | 80,000 |
| 27 | 40,000 | 56,000 | 60,000 | 65,000 | 70,000 | 75,500 | 80,000 | 80,000 |
| 28 | 40,000 | 57,000 | 60,500 | 65,500 | 71,000 | 76,500 | 80,000 | 80,000 |
| 29 | 40,000 | 57,500 | 61,500 | 66,000 | 71,500 | 77,000 | 80,000 | 80,000 |
| 30 | 40,000 | 58,500 | 62,000 | 66,500 | 72,000 | 77,500 | 80,000 | 80,000 |
| 31 | 40,000 | 59,000 | 62,500 | 67,500 | 72,500 | 78,000 | 80,000 | 80,000 |
| 32 | 40,000 | 60,000 | 63,500 | 68,000 | 73,000 | 78,500 | 80,000 | 80,000 |
| 33 | 40,000 | 60,500 | 64,000 | 68,500 | 74,000 | 79,000 | 80,000 | 80,000 |
| 34 | 40,000 | 61,500 | 64,500 | 69,000 | 74,500 | 80,000 | 80,000 | 80,000 |
| 35 | 40,000 | 62,000 | 65,500 | 70,000 | 75,000 | 80,000 | 80,000 | 80,000 |
| 36 | 40,000 | 63,000 | 66,000 | 70,500 | 75,500 | 80,000 | 80,000 | 80,000 |
| 37 | 40,000 | 63,500 | 66,500 | 71,000 | 76,000 | 80,000 | 80,000 | 80,000 |
| 38 | 40,000 | 64,500 | 67,500 | 71,500 | 77,000 | 80,000 | 80,000 | 80,000 |
| 39 | 40,000 | 65,000 | 68,000 | 72,500 | 77,500 | 80,000 | 80,000 | 80,000 |
| 40 | 40,000 | 66,000 | 68,500 | 73,000 | 78,000 | 80,000 | 80,000 | 80,000 |
| 41 | 40,000 | 66,500 | 69,500 | 73,500 | 78,500 | 80,000 | 80,000 | 80,000 |
| 42 | 40,000 | 67,500 | 70,000 | 74,000 | 79,000 | 80,000 | 80,000 | 80,000 |
| 43 | 40,000 | 68,000 | 70,500 | 75,000 | 80,000 | 80,000 | 80,000 | 80,000 |
| 44 | 40,000 | 69,000 | 71,500 | 75,500 | 80,000 | 80,000 | 80,000 | 80,000 |
| 45 | 40,000 | 69,500 | 72,000 | 76,000 | 80,000 | 80,000 | 80,000 | 80,000 |
| 46 | 40,000 | 70,500 | 72,500 | 76,500 | 80,000 | 80,000 | 80,000 | 80,000 |
| 47 | 40,000 | 71,000 | 73,500 | 77,500 | 80,000 | 80,000 | 80,000 | 80,000 |
| 48 | 40,000 | 72,000 | 74,000 | 78,000 | 80,000 | 80,000 | 80,000 | 80,000 |
| 49 | 40,000 | 72,500 | 74,500 | 78,500 | 80,000 | 80,000 | 80,000 | 80,000 |
| 50 | 40,000 | 73,500 | 75,500 | 79,000 | 80,000 | 80,000 | 80,000 | 80,000 |
| 51 | 40,000 | 74,000 | 76,000 | 80,000 | 80,000 | 80,000 | 80,000 | 80,000 |
| 52 | 40,000 | 75,000 | 76,500 | 80,000 | 80,000 | 80,000 | 80,000 | 80,000 |
| 53 | 40,000 | 75,500 | 77,500 | 80,000 | 80,000 | 80,000 | 80,000 | 80,000 |
| 54 | 40,000 | 76,500 | 78,000 | 80,000 | 80,000 | 80,000 | 80,000 | 80,000 |
| 55 | 40,000 | 77,000 | 78,500 | 80,000 | 80,000 | 80,000 | 80,000 | 80,000 |
| 56 | 40,000 | 78,000 | 79,500 | 80,000 | 80,000 | 80,000 | 80,000 | 80,000 |
| 57 | 40,000 | 78,500 | 80,000 | 80,000 | 80,000 | 80,000 | 80,000 | 80,000 |
| 58 | 40,000 | 79,500 | 80,000 | 80,000 | 80,000 | 80,000 | 80,000 | 80,000 |
| 59 | 40,000 | 80,000 | 80,000 | 80,000 | 80,000 | 80,000 | 80,000 | 80,000 |
| 60 | 40,000 | 80,000 | 80,000 | 80,000 | 80,000 | 80,000 | 80,000 | 80,000 |
Values reflect FHWA policy of rounding down when calculated weights fall exactly halfway between 500-pound increments.
Always verify current regulations with Federal (Interstate Highway System) DOT before making shipping decisions.
Permit Information
Requirements & Costs
- Overweight threshold
- 80,000 lbs
- Single trip permit
- $0
- Processing time
- N/A
- Divisible loads
- Not permitted
- Online application
- Not available
Required Documents
Special Vehicle Provisions
federal Bridge Formula
W = 500 x ((LxN)/(N-1) + 12N + 36). Max GVW 80,000 lbs even when formula allows more. Single axle 20,000 lbs. Tandem axle 34,000 lbs.
grandfather Rights
States cannot reduce limits below what was legal on July 1, 1956 (pre-Interstate Highway Act). Higher weights authorized under state law before that date are grandfathered.
idle Reduction
Vehicles with idle reduction technology may increase max GVW and axle weight by up to 550 lbs with proof of fully functional technology.
permit Weights
Natural gas or electric battery vehicles may exceed power unit weight limit by up to 2,000 lbs, max 82,000 lbs GVW. No federal overweight permits exist - states administer all permits.
Contact Information
Permit Office
Hours: Contact state DOT for permits
Official Website
Federal (Interstate Highway System) DOT WebsiteImportant Notes
- Federal limits apply to Interstate Highway System
- States cannot reduce these limits without losing federal funding
- Permits must be obtained from individual states
- Bridge Formula: W = 500 × ((L×N)/(N-1) + 12×N + 36)
Calculate Your Weight Compliance
Use our interactive calculator to check if your truck configuration is compliant with Federal (Interstate Highway System) regulations.
Open Weight CalculatorNeed Help With Federal (Interstate Highway System) Compliance?
Our experts can help you maximize payload while staying compliant.
Get Expert ConsultationSource: 23 USC 127 | Last Updated: 1/15/2025 | Effective: 1/1/2025
Always verify current regulations with official sources before making shipping decisions.