Road base and crushed stone sub-base
Base Course Calculator
Answer first: a 4-inch base course layer under a 20×20 ft driveway needs about 2.5 tons of crushed aggregate. Base course (road base, gravel base, or crushed limestone) is the compacted sub-base layer under concrete, asphalt, and driveways. This calculator gives tons, cubic yards, and cost so you can order the right amount.
20×20 ft driveway at 4 inches compacted
~2.5 tons of base course
Standard 4-in compacted depth for a residential driveway or patio sub-base. Base course compacts 20–25%, so you need extra loose material.
100 sq ft at 6 inches compacted
~2.3 tons
6-in depth for heavy loads or weak subgrade. Use 6-in base under concrete driveways in areas with freeze-thaw cycles.
Material cost reference
$20–$35 per ton delivered
Prices vary by region and quarry distance. Crushed limestone (flex base, road base) typically runs $20–$30/ton. Crushed gravel: $25–$35/ton.
Compaction factor
20–25% shrinkage after compaction
Always order 20–25% more than your finished volume. Loose material compacts significantly — a 5-in loose layer becomes about 4 in compacted.
Interactive workflow
Run the numbers, then save or export the project
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What is base course and what is it used for?
Base course (also called aggregate base course, ABC, DGA, or road base) is a compacted layer of well-graded crushed aggregate placed between the native soil (subgrade) and the finished surface. It is used under concrete slabs, asphalt driveways, paver patios, shed pads, and roads. It distributes load, provides drainage, prevents frost heave, and creates a stable, level surface for whatever goes on top.
What is ABC gravel (aggregate base course)?
ABC stands for Aggregate Base Course — the most common gravel base material in the Southeast US. It is a well-graded mixture of crushed stone from 3/4 inch down to fine dust ("fines"). The larger stones provide load support, and the fines fill the voids, locking everything together when compacted. ABC weighs about 145 lbs per cubic foot. It is called road base, flex base (Texas), DGA (dense graded aggregate), Type 1, or crusher run in different regions.
How much base course do I need for a driveway?
Formula: Length × Width × Depth (in) ÷ 12 ÷ 27 × 1.96 (tons per yd³) × 1.2 (compaction). Example: a 20×20 ft driveway at 4 in compacted = 400 × 0.333 ÷ 27 × 1.96 × 1.2 = 2.5 tons. A longer driveway, 300 × 12 ft at 6 in = 84 yd³ compacted × 1.2 = 101 yd³ to order ≈ 198 tons. Use this calculator to get the exact amount.
How deep should base course be for different applications?
Standard depths: Residential driveway (car traffic): 4 inches compacted. Heavy vehicle driveway: 6 inches. Paver patio: 4–6 inches. Shed pad: 4 inches. Road base for rural roads: 6–12 inches. Parking lot: 6–8 inches. Areas with clay soil or poor drainage benefit from extra depth — 6 inches prevents the classic sinking-after-first-rain problem. Place in maximum 4-inch lifts and compact each lift before adding more.
What is the difference between base course, sub-base, and subgrade?
Three distinct layers from bottom to top: Subgrade is the native soil — it is prepared (graded and compacted) but not imported. Sub-base is an optional lower layer of coarser aggregate (3-inch stone or recycled concrete) used when the subgrade is very weak. Base course (ABC) is the main structural layer directly under the surface. For most residential projects, only base course is needed — sub-base is added for heavy loads or poor soil conditions.
What is DGA (dense graded aggregate)?
DGA (Dense Graded Aggregate) is the engineering specification name for the same material commonly called ABC or road base. It describes a gradation where particle sizes range from large (3/4 in) to fine dust, with specific percentages passing each sieve size. This gradation makes the material compact tightly with few air voids. Local quarries sell it under different names — just ask for "driveway base," "road base," or show them the DGA spec if required by your engineer.
How is base course installed in lifts?
Never place more than 4 inches of base course before compacting. Thicker lifts trap air and do not fully compact, leaving a weak layer. Steps: (1) Spread 4-in loose layer. (2) Compact with plate compactor or roller until no visible movement. (3) If more depth is needed, add another 4-in loose layer and compact again. Each compacted lift = about 3.2 inches after compaction. The formula adds 20% for this compaction shrinkage.
What does base course cost per ton?
Base course (ABC/road base) costs $15–$35 per ton plus delivery in 2026. Texas near quarries: $15–$22/ton. Midwest: $18–$28/ton. Northeast: $22–$40/ton. Delivery adds $50–$150 per load depending on distance. A minimum delivery is usually 5–10 tons. Reddit DIYers advise: "See what a truckload of ABC costs in your area" — quarry proximity is the biggest price driver.
Can I use base course under pavers?
Yes — base course is the standard sub-base for paver patios, walkways, and driveways. Use 4–6 inches of compacted ABC or road base, then 1 inch of coarse sand (bedding sand) on top before laying the pavers. The base provides the structural support; the sand allows for leveling. For large paver projects, 6 inches of base and proper edge restraints prevent the pavers from shifting.
How many tons of base course in a truck load?
A standard dump truck carries 10–14 tons of aggregate base course. A tandem axle truck: 12–16 tons. A triaxle or quad-axle truck: 18–24 tons. When ordering, divide your total tons by the truck capacity to get the number of loads. Example: 20 tons ÷ 14 = 2 truck loads (round up). Most quarries have a minimum delivery of 1 full truck, so small projects may pay a minimum delivery fee.
What is Type 1 aggregate (and is it the same as base course)?
Type 1 is the British Standard (BS EN 13285) specification for sub-base aggregate — equivalent to what Americans call road base or ABC. It is a well-graded crushed aggregate used as a foundation layer under roads, driveways, and structures. If you are in the UK or Canada and your spec says "Type 1 sub-base," use this calculator — the calculation method is identical. Just enter your project dimensions and depth.
How do I convert base course from cubic yards to tons?
Multiply cubic yards by 1.96 to get tons (for ABC/dense grade aggregate at 145 lbs/ft³). To convert tons to cubic yards: divide tons by 1.96. Example: 10 tons of ABC = 10 ÷ 1.96 = 5.1 cubic yards. Different materials have different densities: washed stone is lighter (about 1.4 tons/yd³), rip rap is heavier (about 1.6 tons/yd³). Always confirm density with your local supplier.
Planning disclaimer
Base course calculations include a 20% compaction factor. Actual requirements vary by material gradation, compaction equipment, and subgrade conditions. Verify with your contractor and supplier.