Multiply length × width × depth in feet, divide by 27 for cubic yards, then multiply by 1.55 for tons of 2A modified. A 50 × 12 ft driveway at 4 inches deep needs about 7.4 cubic yards — roughly 11.5 tons — plus 15% for compaction.
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2A Modified Stone Calculator Guide
Ask for “2A modified” at a quarry in Pennsylvania and everyone knows exactly what rolls onto the scale: the PennDOT-specified dense-graded aggregate that underlies most of the driveways, garage pads, and farm lanes in the state. Ask for it two states away and you may get a blank look — not because the product does not exist there, but because it wears a different name. This calculator prices the material itself: 1.55 tons per cubic yard, with a 15% compaction allowance built into the default.
The “modified” in the name is the working part. Plain 2A is a graded stone; the modified version is blended with extra fines so that, compacted damp, it sets up almost like a weak pavement. That behavior — hard crust on top, structural mass below — is what people are really ordering.
What Is 2A Modified Called in Other States?
Dense-graded base stone is the most regionally renamed product in the aggregate business. If you know one column of this table, you know them all:
| Region | Local name | Same essential product |
|---|---|---|
| Pennsylvania | 2A modified | Dense-graded, 3/4 in top size with fines |
| New Jersey / New York | DGA or QP (quarry process) | Yes |
| Virginia | 21A / 21B | Yes |
| North Carolina | ABC (aggregate base course) | Yes |
| Southeast generally | Crusher run | Yes |
| Upper Midwest | Class 5 | Yes |
| Mountain West | Road base | Yes |
Putting 2A Modified to Work
- Car driveways: 4 inches compacted over firm subgrade; 6 inches where the ground stays damp.
- Truck and equipment lanes: 6–8 inches in two compacted lifts, over geotextile on soft soils.
- Shed and hot tub pads: 4–6 inches, screeded level and compacted to refusal.
- Under pavers and walls: 4 inches minimum as the structural course beneath the bedding layer.
- Compact it damp: a light watering before each compactor pass activates the fines and produces the signature hard-set surface.
If your supplier lists the product under its generic name, the crusher run calculator runs the identical math, and mid-Atlantic readers outside Pennsylvania will find their local terminology in the DGA calculator.
Frequently Asked Questions
What is 2A modified stone?
A PennDOT-spec dense-graded aggregate with a top size around 3/4 inch and everything below it down to dust. The full range of sizes lets it compact into a near-solid base, which is why it dominates driveway and pad construction in Pennsylvania.
What is the difference between 2A and 2B stone?
2A modified is dense-graded with fines and compacts tight; 2B is clean washed stone in the 3/4 to 2 inch range that stays open and drains. Base layers get 2A, drainage applications get 2B — they are complements, not substitutes.
How much does a yard of 2A modified weigh?
About 1.55 US tons (3,100 lb) per cubic yard, on the heavy end for aggregate because the fines fill what would otherwise be air space between stones.
Is 2A modified the same as crusher run?
Functionally yes — both are dense-graded crushed stone with fines that compact into a structural layer. 2A modified is the PennDOT designation used in Pennsylvania and nearby states; elsewhere the equivalent product sells as crusher run, DGA, or road base.