The federal axle and gross weight limits, the bridge formula and the state spring thaw rules that decide whether your order arrives on one truck or two.
Use the Gravel Calculator — work out the tons a load actually has to carry.
The calculators here answer how much material. They do not answer what the yard asks next: whether that much fits on one truck. That is a weight-law question, and the numbers are published.
For the Interstate System and reasonable access to it, 23 CFR 658.17 sets three ceilings, and 23 U.S.C. 127(a) is their statutory basis: it makes half of a state's National Highway Performance Program apportionment under section 104(b)(1) conditional on the state allowing them. These are regulatory values, not measured properties of anything, and they do not move with the material.
A cubic yard of wet loam and a cubic yard of washed stone weigh very different amounts; those figures, with their sources, sit on the gravel calculator rather than here. Both are measured against the same 80,000 pounds.
Paragraph (g) is the part people misjudge. Those weights, and the bridge formula figures, are inclusive of all tolerances, enforcement or otherwise. The only exception is a scale allowance when portable wheel-load weighers are used, and the regulation caps it at 5 percent. There is no built-in margin to spend.
| Limit | Figure | Paragraph of 23 CFR 658.17 |
|---|---|---|
| Gross vehicle weight | 80,000 lb, unless the bridge formula dictates less | (b) |
| Any one axle, including one axle of a group | 20,000 lb | (c) |
| Tandem axles | 34,000 lb | (d) |
| Group of two or more consecutive axles | Bridge Gross Weight Formula | (e) |
| Enforcement tolerance | None; portable-scale allowance capped at 5 percent | (g) |
Paragraph (e) carries what it calls the Bridge Gross Weight Formula. The eCFR renders it as an image, so the readable statement is the statute: 23 U.S.C. 127(a)(2) gives W = 500(LN/(N-1) + 12N + 36), where W is the overall gross weight on any group of two or more consecutive axles to the nearest 500 pounds, L is the distance in feet between the extremes of that group, and N is the number of axles in the group.
Read it as a spacing rule rather than a weight rule. The allowance for a group rises as the axles move apart and as axles are added, because a short group concentrates its load over a shorter span of whatever it is crossing. The regulation then names one exception: two consecutive sets of tandem axles may each carry 34,000 pounds if the overall distance between the first and last axle is 36 feet or more. It closes with a hard stop: in no case shall the total gross weight of a vehicle exceed 80,000 pounds.
This is why a loaded truck can sit under 80,000 pounds and still be illegal. Aggregate and fresh concrete can reach an axle-group limit before the body is full: legal on gross, over on the group.
Paragraph (a) of 658.17 is a scope statement, and it matters. The section applies to the National System of Interstate and Defense Highways and reasonable access to it, and paragraph (f) bars a state from enforcing anything lower than those figures on the Interstate System. Neither reaches the county road, the township lane or the last hundred feet of shared driveway; those are governed by state and local law, which can be stricter and often is.
Congress also preserved what states already allowed. 23 U.S.C. 127(a)(4) bars Congress from denying apportionment to a state that allows operations it determined could lawfully be conducted on 1 July 1956, with the axle-group case pinned instead to the enactment of the Federal-Aid Highway Amendments of 1974; Michigan's own date is 1 May 1982, under paragraph (a)(7). The regulation adds named route exceptions, such as coal, log and pulpwood vehicles on Interstate 68 in Allegany and Garrett Counties, Maryland, at 658.17(j). These are named exceptions, not a general rule.
Then there are bridges. 23 CFR 650.313(l) requires the State transportation department or Federal agency running the inspection programme to post or restrict a bridge when unrestricted legal loads exceed what its rating allows, no later than 30 days after the rating that shows the need, and paragraph (m) requires closure when gross live load capacity falls below 3 tons. One posted bridge between the quarry and your gate can set the size of every load you receive.
Roads in cold states lose strength for a few weeks as frost comes out of the ground, and states cut posted weights in response. The reductions are published, they differ by state, and they are not interchangeable.
Michigan issues numbered Spring Weight Restriction Bulletins. Bulletin #1, dated 17 February 2026, imposed restrictions from 6 p.m. that day; Bulletin #8, dated 15 May 2026, lifted the last of them at 7 a.m. Each bulletin in the series separates routes designated All Season on the MDOT Truck Operators Map, where there is no reduction in legal axle weight, from routes designated Seasonal, where rigid and flexible pavements are cut by different published amounts. The bulletins add that single trip permits will not be issued for overweight loads in the restricted area.
Minnesota puts its version in statute rather than in a bulletin. Section 169.87, subdivision 2 caps single-axle weight during the season at one figure for unpaved roads and a higher one for paved. Paragraph (b) then adds a separate reduction for gross weight on consecutive axles on an unpaved road, and says expressly that this reduction does not apply to the gross vehicle weight. Those are two different bases, and the drafting keeps them apart. MnDOT sets the dates by frost zone, publishing 2026 starts from 3 March and ends from 20 April to 15 May.
| Instrument | Applies to | Figure as published |
|---|---|---|
| MDOT Spring Weight Restriction Bulletins, 2026 series | Routes designated Seasonal | Weight reduction of 25 percent for rigid pavements, 35 percent for flexible pavements |
| The same bulletins | Routes designated All Season | No reduction in legal axle weight |
| Minn. Stat. 169.87, subd. 2(a) | Single axle | Five tons on an unpaved street or highway; ten tons on a paved one |
| Minn. Stat. 169.87, subd. 2(b) | Gross weight on consecutive axles, unpaved roads only | Allowed figure multiplied by five divided by nine; expressly not applied to gross vehicle weight |
The other surprise on a scale ticket is water. A load is weighed as it sits, water included, so a stockpile rained on for two days crosses the weighbridge heavier than the same volume from the same pile in a dry week. No standard publishes a figure for that difference, because it belongs to one stockpile on one morning. The measured densities that do have sources, and the moisture condition each was measured at, are on the gravel calculator and the topsoil calculator.
The instinct here is to ask for an overweight permit, and it does not apply. 23 CFR 658.17(h) lets states issue special permits without regard to axle, gross or bridge formula limits for nondivisible vehicles or loads, and 23 CFR 658.5 defines nondivisible as a load which, if separated into smaller loads, would compromise the intended use of the vehicle, destroy the value of the load, or require more than 8 work hours to dismantle. Bulk stone, soil and fresh concrete fail all three tests. Half a load of stone is still stone and still does its job, which is why the yard splits it instead.
One number here is published nowhere, and it is the one you want: how much your supplier's truck carries. Payload is the legal limit on the route minus that truck's tare weight, and tare belongs to one vehicle: its body, its lift gear, its drum, its fuel. No federal regulation, no state DOT bulletin and no consensus standard states it. It comes off the supplier's own certified scale tickets.
So two questions are worth asking when you order: what does the truck weigh empty, and which routes is it coming in on. The answer to those is your split. Work out the quantity first with the calculators, then let the yard tell you how many trips that quantity is.