Montana Oversize Permit Cost: Worked Examples
Four worked Montana moves: the flat size trip fee, bridge-formula overweight by route distance, excess axle weight math, and a superload.
By Evan Reid, Founder of Haul Handbook · Updated Sep 28, 2026 · 12 min read
Montana prices size and weight on two separate tracks. A trip permit for size costs
$10.00under Mont. Code Ann. 61-10-124(1), whether the load is 9 feet wide or 17, and whether it runs 20 miles or 600. Weight is where the math lives. A load that breaks the bridge formula pays by route distance, and a load over legal axle weights pays by the pound and the mile. Every current figure renders with its official source on the Montana oversize and overweight permits page. This guide runs four moves through the rules so the numbers read like a quote. To see where your load crosses a legal line in the first place, try the oversize permit cost estimator.
How Montana builds the number
Start with the legal envelope. Montana allows 8 feet 6 inches of width (61-10-102) and 14 feet of height (61-10-103). A semitrailer can run 53 feet, and a tractor-semitrailer has no overall length limit under 61-10-104. A single truck tops out at 55 feet, and most other combinations at 75 feet.
Weight works differently from most states. Montana has no flat 80,000-pound gross cap. Mont. Code Ann. 61-10-107 sets 20,000 pounds per single axle and 34,000 pounds per tandem, then applies the bridge formula to every vehicle and axle group. MDT's gross weight chart tops out at 131,060 pounds for reducible loads, and MDT's permitting FAQ says a truck over 80,000 pounds needs no special permit when it is licensed for the weight and legal on axles and the bridge formula. That license is the GVW fee tied to your Montana IRP registration, a separate cost from any permit.
Past those lines, four charges build the permit price:
- Size trip permit: $10.00 per trip for any load over 8 feet 6 inches wide, 75 feet long, or 14 feet high, a single unit over 55 feet, or a single trailer over 53 feet.
- Overweight on bridge: for a load legal on every axle but over the bridge formula, $10.00 for a route up to 100 miles, $30.00 for 101 to 199 miles, and $50.00 for 200 miles or more.
- Excess axle weight: for a non-divisible load over legal axle weights, $3.50 per 5,000 pounds of excess for each 25 miles of route.
- Tolerance permit: MCS enforcement officers alone issue the 10 percent tolerance permit, at $10.00, to get a load to the first place it can be adjusted or to its destination.
Size and weight bill separately, so a load that is both wide and heavy buys both. Every trip permit is void once the load leaves Montana, and MDT requires at least $1,000,000 combined single limit liability coverage for oversize permits. The Montana trucking insurance requirements page covers the rest of the coverage stack.
Worked example 1: the 14-foot load and the road it takes
A contractor moves a 14-foot-wide modular building section 180 miles, first on I-90 and then on a two-lane state highway to the site. It stands 13 feet 6 inches high and sits within legal weight. Width is the only line crossed, so the permit costs one flat $10.00. The distance never enters the size fee.
Here is why the road still sets the real cost. MDT's permit restrictions set pilot vehicles by highway type:
- On the interstate, no pilot vehicle is required until a load passes 16 feet 6 inches wide, and travel is open around the clock up to 18 feet wide.
- On non-interstate highways, one front pilot vehicle starts over 12 feet 6 inches wide.
- On non-interstate highways, a load over 10 feet wide moves in daylight only.
So the section runs I-90 at night with no pilot, then waits for daylight and picks up a front pilot at the exit. Loads over 10 feet wide also carry the yellow OVERSIZE LOAD sign and flashing amber lights on the load and the power unit.
Holidays close part of the route. On New Year's Day, Memorial Day, the Fourth of July, Labor Day, Thanksgiving and Christmas, interstate loads up to 18 feet wide may still move, but non-interstate loads over 12 feet 6 inches wide may not. A holiday that lands on a Friday or Saturday closes Friday through Sunday, and Thanksgiving closes Thursday through Sunday. This load could reach the exit on a holiday weekend and then sit until Monday.
Worked example 2: the bridge-formula load and the 100-mile line
A non-divisible transformer rides on a trailer where every single axle stays under 20,000 pounds and every tandem under 34,000, but the gross is over what the bridge formula allows for that axle spacing. The load is legal on axles and over on the bridge, so it pays the distance-banded charge instead of the per-pound math.
On a 150-mile route, the fee is $30.00. Let's break down how the route moves it:
The jump sits at the band edges. MDT's handbook charges the lowest band up to and including 100 miles, so a route of 101 miles triples the fee. If the delivery point can be reached from a yard inside 100 miles, the routing is worth checking before you file.
Bridges also add conditions. On non-interstate highways, a bridge centerline move needs at least two pilot vehicles, one front and one rear, and a bridge slowdown move needs one rear pilot, unless the route crosses no bridges. If the transformer is also over 8 feet 6 inches wide, add the size trip permit on top.
Worked example 3: the heavy excavator and the excess axle math
A lowboy hauls a tracked excavator 230 miles. At the scale, the tractor's rear tandem weighs 38,000 pounds and the trailer tandem 42,000 pounds. Against the 34,000-pound tandem limit, that is 4,000 pounds over on the tractor and 8,000 over on the trailer. MDT's handbook example adds the excess on each axle group into one total, so this load carries 12,000 pounds of excess.
The fee is
$3.50per 5,000-pound increment for each 25-mile increment, and the handbook rounds both up to the next increment. The math:
- Weight: 12,000 pounds rounds up to 15,000, which is three increments.
- Charge per 25 miles: 3 x $3.50 = $10.50.
- Mileage: 230 miles rounds up to 250, which is 10 increments.
- Overweight fee: 10 x $10.50 = $105.
If the excavator's tracks make the load 11 feet wide, the size trip permit bills on top of that, for $115 in all.
Rounding is where the money moves. At 251 miles, the route rounds to 275, and the fee becomes 11 x $10.50 = $115.50. At 15,001 pounds of excess, the weight rounds to 20,000 and each segment costs $14, so the same 230-mile trip costs $140. Weigh each axle group before you buy, because a few hundred pounds past an increment buys the whole next one for every segment of the trip.
MDT's handbook checks its own table the same way: 31,250 pounds of excess rounds to 35,000, or $24.50 per segment, and 389 miles rounds to 400, or 16 segments, for a $392 permit. Past 100,000 pounds of excess, the table caps at $70 per segment plus $3.50 for each 5,000 pounds, or part of 5,000, beyond that.
A carrier who moves the same heavy equipment all year can buy a term overweight permit instead. MDT sells it by excess-weight band from 5,000 to 40,000 pounds, for a year or by the quarter, and bands of 15,000 pounds and up need a vehicle weight analysis first. The band prices sit on the Montana oversize and overweight permits page, and the break-even is the band price divided by what one trip costs you.
Worked example 4: the 160-foot load and the superload line
A 160-foot bridge girder load runs on a non-interstate highway. Length alone makes it a superload: MDT requires a superload application for any load over 18 feet wide, 17 feet high, or 150 feet long. At 160 feet it falls in Class 1, which runs past 150 feet up to 200 feet long (or past 18 up to 34 feet wide, or past 17 up to 24 feet high).
The fee under 61-10-124(1) stays the per-trip size charge of $10.00. The cost of this move lives in the conditions instead:
- Approval: the MDT district administrator or a designee approves it, with a decision due within two working days of a complete Class 1 application. Class 1 approvals are good for 60 days. Superload correspondence goes to mdtmcssuperload@mt.gov.
- Pilot vehicles: one rear pilot on non-interstate highways from 150 up to 200 feet, and a front and a rear pilot past 200 feet.
- Hours: daylight only, since non-interstate loads over 150 feet long lose night travel.
- Weekends and holidays: none. Non-interstate loads over 150 feet long get no weekend travel and may not move on holidays.
- Notice: superload moves must notify local law enforcement, fire and ambulance services before travel.
A 130-foot version of the same load avoids all of that. It sits under the 150-foot superload line and needs no length pilot, and if it also stays within 10 feet wide and 15 feet 6 inches high, it travels non-interstate highways around the clock. Class 2 covers anything past the Class 1 limits, with a decision due within five working days.
The term permit for repeat moves
A carrier who runs oversize often can skip the trip permits. The term oversize permit costs
$75.00under 61-10-124(1) and covers loads up to 15 feet wide, 15 feet 6 inches high and 95 feet long. At the trip fee, the eighth trip of the year is where it pays.
Timing matters more than the fee. Term permits expire December 31 with no grace period, so a permit bought in October covers three months. They go to power units licensed in Montana, apportioned through Montana IRP, or from a reciprocal jurisdiction. Nothing past 15 feet wide or 95 feet long qualifies, because 61-10-124(2)(a) limits those loads to trip permits, with separate term permits for 100-foot interstate doubles and for non-divisible loads up to 120 feet long.
Winter hauling has its own option. The wintertime weight permit allows 10 percent excess weight on non-interstate highways from December 1 through March 7, up to 132,000 pounds, and MDT suspends it early when roads thaw.
Next steps before you buy
MDT Motor Carrier Services sells permits through the MT eTRIPS system at etrips.mtmdt.us, by phone at (406) 444-7262, and at weigh stations after hours. Every permit rides in the truck as a legible printed or electronic copy, and any writing on it voids it. County and city roads need their own local permit.
For a quick quote: one flat size fee per trip, a bridge-formula charge set by route distance, and an excess axle charge built from 5,000-pound and 25-mile increments, both rounded up. Compare Montana against the same move elsewhere on the oversize permit costs by state table, and see every other credential the state expects at Montana trucking permits.
FAQ
How much does a Montana oversize permit cost?
Mont. Code Ann. 61-10-124(1) sets 10 dollars for each trip permit for size and 75 dollars for each term permit for size. The trip fee is flat: it does not grow with distance or with how far the load runs past the legal width, height, or length. Overweight is charged separately, and every trip permit is void once the load leaves Montana.
How is the Montana overweight permit fee calculated?
It depends on which limit the load breaks. A non-divisible load that is legal on every axle but over the bridge formula pays 10 dollars for a route up to 100 miles, 30 dollars for 101 to 199 miles, or 50 dollars for 200 miles or more. A non-divisible load over legal axle weights pays 3 dollars 50 cents per 5,000 pounds of excess axle weight for each 25 miles of route, with both weight and mileage rounded up to the next increment. A load 12,000 pounds over on a 230 mile route pays 105 dollars.
Does Montana have an 80,000 pound gross weight limit?
No. Montana has no flat gross cap. Mont. Code Ann. 61-10-107 sets 20,000 pounds per single axle and 34,000 pounds per tandem and applies the bridge formula to every vehicle and axle group, and MDT's gross weight chart tops out at 131,060 pounds for reducible loads. MDT says no special permit is needed over 80,000 pounds when the truck is licensed for the weight and legal on axles and the bridge formula.
When does a Montana oversize load need a pilot vehicle?
It depends on the road. On non-interstate highways, one front pilot starts over 12 feet 6 inches wide, two over 16 feet 6 inches, three over 18 feet, and four over 24 feet. On the interstate, one rear pilot starts over 16 feet 6 inches wide and two side by side over 18 feet. Loads over 17 feet high need a front pilot with a height pole, and non-interstate loads over 150 feet long need a rear pilot.