Truck weight limit checker: legal on every axle?
Enter your axle weights and the distance between axles. The truck weight limit checker tests each axle group, the gross and the bridge formula against federal Interstate limits.
Defaults are an example load. Weigh on a certified scale; these numbers are only as good as the weights you enter.
Legal on the Interstate
| Check | Weight | Limit |
|---|---|---|
| Steer axle | 12,000 lb | 20,000 lb |
| Drive tandem | 34,000 lb | 34,000 lb |
| Trailer tandem | 33,500 lb | 34,000 lb |
| Gross (bridge, 5 axles over 55 ft) | 79,500 lb | 80,000 lb |
| Drives + trailer (bridge, 4 axles over 40 ft) | 67,500 lb | 68,500 lb |
Gross 79,500 lb: within every federal axle, gross and bridge limit.
POSTED: eCFR, 23 CFR 658.17(b) · checked Oct 2026
Our dispatchers check weight against your truck before they offer a load, and plan loads around your hours and home time. Dispatch runs 5% of gross for one truck, and you confirm every load.
By Nathan Beck · Updated October 2026
Being under 80,000 lb gross is not the same as being legal. One heavy tandem, or axles too close together, can put you over a limit while the total looks fine. This truck weight limit checker tests each part of the federal rule: single axles, tandems, gross weight and the bridge formula, and tells you which one is the problem.
DOT weight limits per axle
On the Interstate system and reasonable access to it, federal rules set:
- Single axle: 20000 lb.
- Tandem axle: 34000 lb.
- Gross: 80000 lb, unless the bridge formula sets less.
- No built-in tolerance: federal limits include all enforcement tolerances (portable scales may allow up to 5%).
States must allow these on the Interstate and set their own limits on other roads. We have not verified state limits for non-Interstate routes yet, so the tool shows the federal numbers and says so.
POSTED: eCFR, 23 CFR 658.17 (Weight) · checked Oct 2026
The bridge formula
Bridges are stressed by weight concentrated over a short span, so the federal rule limits the weight on any group of axles by how far apart they are: W = 500 (LN/(N-1) + 12N + 36): W = max weight in lb on a group of 2+ consecutive axles, L = feet between the group's outer axles, N = axles in the group. Two consecutive tandems may carry 34,000 lb each if the first and last of those axles are 36 feet or more apart. That is why a five-axle truck needs about 51 feet from steer to last axle to reach 80,000 lb.
A working APU or idle reduction unit earns up to 400 lb extra (gross, axle, tandem or bridge) on top of the limits, if you carry its weight certification.
How it is calculated
- Axle groups: steer and drive as single axles or tandems, and the trailer tandem, each against its limit.
- Gross: all axles against the bridge formula for every axle over the full wheelbase, capped at 80,000 lb.
- Drives plus trailer: the four rear axles against the bridge formula over their spacing, or 68,000 lb with 36 feet or more.
- APU: adds 400 lb to each limit when ticked.
- Result: legal, or the check that is furthest over.
What a good result and a bad result look like
A good result is legal on every line with a margin, weighed on a certified scale after loading. A bad result is a gross that looks fine with one axle group over, or a short wheelbase that the bridge formula will not let carry the load. Overweight divisible loads cannot be permitted; only loads that cannot be broken down can get a state permit.
Scales are where this gets checked, and our guide to the truck weigh station explains what happens there. For loads over size as well as weight, use the oversize load checker, and the semi truck and trailer dimension fit checker for whether the freight fits at all. Heavy loads also take longer to stop and park; some states have few truck spaces, as truck parking capacity by state shows.
Loads that fit your truck
Our dispatchers check weight and size against your truck before a load reaches you, and plan loads around your hours and home time. If a load would put you over, it does not get offered. You confirm every load and get the rate con yourself. Read how it works for owner operators, or apply in about two minutes.
Questions about this calculator
What are the DOT weight limits per axle?
On the Interstate system, federal rules set 20,000 lb on any single axle and 34,000 lb on a tandem, with 80,000 lb gross unless the bridge formula sets less. Those limits include all enforcement tolerances. States enforce them on the Interstate and set their own limits on other roads, which can be different, so check the state for non-Interstate routes.
What is the semi truck weight limit?
80,000 lb gross on the Interstate for a standard five-axle tractor-trailer, as long as the axles are spaced far enough apart under the bridge formula. Five axles need about 51 feet between the first and last axle to reach 80,000. Heavier loads need a state permit, and permits are for loads that cannot be divided.
What is the box truck weight limit?
It depends on the truck's weight rating and axles. Federal axle limits are the same for any vehicle: 20,000 lb on a single axle and 34,000 on a tandem. A box truck must also stay within its maker's GVWR. A 26-foot box truck rated at 26,000 lb or less needs no CDL; at 26,001 lb or more it needs a Class B CDL.
Can I get fined at a weigh station for being slightly over?
Yes. Federal rules say the limits include all tolerances, so there is no automatic free margin, though portable scales may allow a small accuracy allowance. Many states fine by the pound over. If a scale shows one axle heavy and the gross is fine, sliding the tandems or the fifth wheel often fixes it on the spot.
PARK BY: PLANNED WITH YOU
Loads checked against your truck before you see them
We check weight and size first. You approve every load.