Road base calculator for Montana

For a 100-foot lane that is 10 feet across and 6 inches deep after compaction, plan on about 31 tons of road base. Lane quantities add up fast, and free delivery is especially useful when 30 tons would otherwise cost nearly as much to haul as the material. Road base combines graded crushed stone with fines and weighs about 3,000 lb per cubic yard. It compacts into a firm layer for roads, driveways, and equipment yards. Where specifications permit, this calculation also applies to recycled crushed concrete base.

Lane calculations

1. For lanes, take the centerline length and average the width. For pads, multiply length by width.
2. Allow 4 inches compacted for light residential use, 6 for regular traffic and delivery trucks, and 8-12 beneath equipment or on soft subgrade.
3. Divide cubic feet by 27 for yards; multiply by 1.5 for tons; leave +10% for compaction.

Coverage and lane totals

Building a lane for the next winter

• Clear away organic material before placing the base. Putting stone over topsoil lets mud work upward through it, regardless of how deep the layer is.
• Lay woven geotextile first where the subgrade is wet or soft, then place the stone. It adds useful reinforcement to a lane at low cost.
• Keep each lift at 4 inches or less and roll it before adding the following lift.
• Build a 2-3% crown away from the centerline so water drains off the edges instead of entering the base.
• For a neat travel surface with less dust, finish with #57 or driveway gravel.
• Moving 20-plus tons by hand can take a week. Budget for a skid steer or a tractor with a box blade, which can handle the work in an afternoon.

Example: a 100-foot farm lane

At 6 inches, one hundred by ten feet works out to 1,000 x 0.5 = 500 cubic feet = 18.5 cubic yards, or about 28 tons and 30-31 after allowing for compaction. Plan on two tandem loads. Put two drop points along the lane instead of one pile at the gate, so material is closer to where it needs spreading.

Pads for RVs, containers, and equipment

Use the same calculation for pads, but choose depth for axle weight rather than the calendar. A 12 x 40 RV pad at 6 inches compacted needs about 12 tons. A 20 x 40 equipment yard at 8 inches takes 27. Shipping containers put their load on four corners, so use a full 8 inches plus fabric for container pads, even on sound ground, to limit corner settlement by spring.

Recycled concrete road base

Virgin road base and recycled concrete base use the same calculation. Recycled concrete can compact and carry load similarly, and may cost less. Check county requirements first, since some specifications call for virgin aggregate. For private lanes and pads, use the same 1.5 tons per yard, lift placement, and crown.

Road base by ton or lane

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