Concrete Calculator for Driveways: Cost and Volume Estimation
A concrete driveway is a significant investment — typically the largest single concrete pour on a residential property. Getting the volume, thickness and cost estimation right before you order saves money, prevents short loads, and ensures the slab performs for decades. This guide covers every factor you need to consider.
Step 1: Measure the driveway area
Driveways come in several shapes. Calculate the area depending on the layout:
- Rectangular (most common): Area = Length × Width. A 6 m × 3 m driveway = 18 m².
- T-shaped or flared: Split into rectangles and triangles. Calculate each section separately and add them together.
- Curved: Approximate with a series of rectangles, or measure the average width and multiply by the length.
- On a slope: The area is the horizontal plan area, not the sloped surface area. The slope only affects the thickness slightly — the volume difference is negligible for typical residential gradients.
Step 2: Choose the right thickness
Driveway thickness is more critical than for any other residential slab because it must support vehicle loads:
| Vehicle type | Minimum thickness | Recommended |
|---|---|---|
| Cars and SUVs only | 100 mm (4″) | 125 mm (5″) |
| Light trucks, vans | 125 mm (5″) | 150 mm (6″) |
| Heavy vehicles, RVs | 150 mm (6″) | 175 mm (7″) |
The extra 25 mm from 100 to 125 mm increases concrete volume by 25% but roughly doubles the load capacity. For most homes, 125 mm is the sweet spot.
Step 3: Calculate the volume
Volume = Area × Thickness
For a 6 m × 3 m driveway at 125 mm:
Volume = 18 × 0.125 = 2.25 m³
Add 5% waste: 2.25 × 1.05 = 2.36 m³
At this volume, ready-mix delivery is strongly recommended over bagged concrete (you'd need ~236 × 20 kg bags).
Use the Concrete Calculator to get this instantly — enter length, width and thickness, and it handles the conversions and waste allowance.
Step 4: Estimate the cost
Concrete pricing varies by location, but typical ranges are:
| Component | Typical cost (AU) | Typical cost (US) |
|---|---|---|
| Ready-mix concrete (25 MPa) | $200–$280/m³ | $130–$180/yd³ |
| Delivery fee (short load) | $50–$120 | $40–$100 |
| Reinforcement mesh (F72) | $15–$25/m² | $10–$18/yd² |
| Sub-base gravel (compacted) | $40–$70/m³ | $25–$45/yd³ |
| Finishing (exposed aggregate, colour) | $50–$120/m² | $35–$90/yd² |
Prices are indicative only — obtain quotes from local suppliers for accurate figures.
For our 2.36 m³ example at $250/m³ plus $80 delivery:
Concrete: 2.36 × $250 = $590 + delivery $80 = $670
Mesh: 18 m² × $20 = $360
Sub-base: ~1.8 m³ × $55 = $99
Total (materials only): ~$1,129
If you're hiring a contractor for excavation, formwork, pouring and finishing, add $60–$120/m² in labour — bringing the total to roughly $2,200–$3,300 for an 18 m² driveway.
Step 5: Base preparation
The sub-base is just as important as the concrete itself. A poorly prepared base will settle, causing the slab to crack and shift:
- Excavate to a depth of slab thickness + sub-base depth (e.g., 125 + 75 = 200 mm below finished level).
- Lay geotextile fabric over the subgrade to prevent the sub-base mixing with the soil.
- Spread and compact road base (75–100 mm) in 50 mm layers using a plate compactor. Each layer should be compacted to at least 95% modified Proctor density.
- Set up formwork with 50 × 100 mm timber, staked at 600 mm intervals. The top of the formwork sets the finished slab level.
- Place reinforcement — F72 mesh (6 mm bars at 200 mm centres) on 20 mm bar chairs. Wire all laps. For heavy vehicle use, consider SL82 mesh (8 mm bars).
- Schedule the pour — concrete must be placed within 90 minutes of batching. Have at least two people on site for a driveway pour.
Step 6: Drainage considerations
A driveway that traps water will deteriorate quickly. Ensure a minimum 1% fall (1:100) away from the house or toward a drain. For a 6 m driveway, that's a 60 mm drop from one end to the other. If the natural slope doesn't allow this, consider a surface drain (trench grate) across the driveway at the low point.
Common driveway concrete mistakes
- Skimping on thickness — 100 mm is the bare minimum for cars. Hairline cracks become structural cracks under load.
- No sub-base — pouring directly on soil or clay guarantees settlement cracks within 1–2 years.
- No control joints — saw cut within 4–18 hours of pouring (see our saw cut guide).
- Adding water on site — suppliers may ask if you want to "wet it up". Say no — every litre of extra water reduces strength.
- Pouring in extreme heat — above 32°C, concrete sets too fast and is prone to plastic shrinkage cracks. Pour early morning in summer.
Calculate your driveway concrete now
Use the Concrete Calculator to get instant volume, bag count and mix estimates for your driveway. Enter your dimensions, set the waste allowance to 5–10%, and use the advanced options for mix design and saw-cut spacing guidance.