Crushed Concrete Calculator: How Much Base Material Do You Need?
What Is Crushed Concrete?
Crushed concrete (also called recycled concrete aggregate or RCA) is old concrete that’s been processed through a crusher into gravel-sized pieces. It’s widely used as a base material under new slabs, as driveway surfacing, and as fill material. It’s cheaper than new crushed stone and considered an environmentally friendly alternative to virgin aggregate.
Crushed Concrete Calculator Formula
Calculating how much crushed concrete you need uses the same volume formula as any fill material:
Tons needed = (Length × Width × Depth in feet) ÷ 27 × 1.35
The 1.35 factor converts cubic yards to tons, since crushed concrete weighs approximately 2,700 lbs (1.35 tons) per cubic yard when compacted.
Step-by-Step Calculation
- Measure your area in feet (length × width)
- Decide your depth (typically 4–6 inches for base, 2–3 inches for top dressing)
- Calculate cubic feet: L × W × (depth in inches ÷ 12)
- Convert to cubic yards: divide by 27
- Convert to tons: multiply by 1.35
- Add 10% for compaction and waste
Example: Driveway Base Layer
For a 12×40 foot driveway at 6 inches of crushed concrete:
- Volume = 12 × 40 × (6÷12) = 240 cu ft
- Cubic yards = 240 ÷ 27 = 8.89 yd³
- Tons = 8.89 × 1.35 = 12.0 tons
- With 10% extra = 13.2 tons
Coverage Rates: Crushed Concrete
| Depth | Coverage per Ton | Coverage per Cubic Yard |
|---|---|---|
| 2 inches | 100–120 sq ft | 135–162 sq ft |
| 3 inches | 65–80 sq ft | 90–108 sq ft |
| 4 inches | 50–60 sq ft | 67–81 sq ft |
| 6 inches | 33–40 sq ft | 45–54 sq ft |
| 12 inches | 17–20 sq ft | 22–27 sq ft |
Coverage varies based on particle size and compaction rate.
Common Uses for Crushed Concrete
As a Base Layer (Under New Concrete)
The most common use. A 4–6 inch layer of compacted crushed concrete provides excellent drainage and a stable base under new concrete slabs. It’s often cheaper than crushed limestone or gravel.
Driveway Surfacing
Crushed concrete makes an affordable driveway surface at 4–6 inches thick. It compacts well, drains water, and is significantly cheaper than poured concrete or asphalt. Best for rural properties and long driveways.
Fill Material
For filling low areas, old foundations, or raising grade. Use larger pieces (1½”–3”) for deep fills, then top with finer crushed concrete (¾” minus) for a smooth surface.
French Drain Backfill
The angular particles and good drainage properties make crushed concrete suitable for surrounding French drain pipes, though washed gravel is still preferred for the pipe zone.
Crushed Concrete vs. Gravel vs. New Stone
| Material | Cost per Ton | Cost per Yard | Best For |
|---|---|---|---|
| Crushed concrete (RCA) | $10–$25 | $15–$35 | Base layers, fill, driveways |
| Crushed limestone | $25–$50 | $35–$70 | Base layers, drainage |
| Pea gravel | $30–$55 | $40–$75 | Drainage, landscaping |
| ¾” clean stone | $35–$60 | $50–$80 | Drainage, French drains |
| Decomposed granite | $40–$65 | $55–$90 | Pathways, patios |
Prices vary significantly by region and distance from the quarry/recycling facility.
Crushed Concrete Sizes Explained
| Size | Particle Range | Use |
|---|---|---|
| Minus 3/4” | Dust to ¾” | Top dressing, compactable base |
| 3/4” clean | ¾” uniform | Drainage, pipe bedding |
| 1½” minus | Dust to 1½” | Driveway base, fill |
| 2”–3” rip-rap | 2”–3” chunks | Deep fill, erosion control |
| 3/8” minus | Dust to 3/8” | Fine top coat, paver base |
For base layers under concrete, use ¾” minus — it has a mix of fine and coarse particles that compact together into a solid base.
Tips for Using Crushed Concrete
-
Compact in lifts — Don’t dump 6 inches and compact once. Place 3-inch lifts and compact each separately with a plate compactor.
-
Wet before compacting — Moisture helps the fines bind together. Spray lightly between lifts.
-
Check pH — Crushed concrete is alkalite (pH 11–12). Don’t use it near acid-loving plants or where water will run into garden beds.
-
Source matters — Ask your supplier what the source material was. Reinforced concrete rubble is fine; material from contaminated sites is not.
-
Allow settling time — If using as a base under new concrete, let compacted crushed concrete settle for at least 24 hours (longer is better) before pouring.
Calculate Your Project
While our main calculator at freeconcretecalc.com is designed for poured concrete projects, you can use the slab calculator to figure out the cubic footage for a crushed concrete base layer. Enter the area dimensions and depth, then convert the cubic feet result to tons by dividing by 20 (approximate: 1 ton covers 20 cu ft of crushed concrete at loose fill).
For calculating the poured concrete that goes on top of your crushed base, our free concrete calculator gives you instant volume, bag counts, and cost estimates for slabs, footings, post holes, and more.