How to Calculate Asphalt Quantity
Calculating asphalt quantity is a three-step process: calculate the area, convert to volume, then convert to weight (tonnes). Let's walk through it step by step.
Step 1: Calculate the Area (m²)
Area = Length × Width
For irregular shapes, divide the area into rectangles and triangles, calculate each, and sum them.
Example: A driveway 20 metres long and 3 metres wide:
Area = 20 × 3 = 60 m²
Step 2: Calculate the Volume (m³)
Convert the layer thickness from millimetres to metres, then multiply by the area.
Volume = Area × (Thickness in mm ÷ 1,000)
Example: 50mm thick asphalt over 60 m²:
Volume = 60 × (50 ÷ 1,000) = 60 × 0.05 = 3.0 m³
Step 3: Calculate the Weight (tonnes)
Weight = Volume × Density ÷ 1,000
Use the appropriate density for your material. For Hot Mix Asphalt, use 2,320 kg/m³.
Example:
Weight = 3.0 × 2,320 ÷ 1,000 = 6.96 tonnes
Step 4: Add Waste Factor
Always add 5–10% for compaction and trimming waste.
Final Weight = Weight × (1 + Waste % ÷ 100)
Example (5% waste):
Final Weight = 6.96 × 1.05 = 7.3 tonnes
Complete Worked Example: Driveway
| Parameter | Value |
|---|---|
| Length | 20 m |
| Width | 3 m |
| Thickness | 50 mm |
| Material | Hot Mix Asphalt |
| Density | 2,320 kg/m³ |
| Waste Factor | 5% |
Calculation:
- 1Area = 20 × 3 = 60 m²
- 2Volume = 60 × 0.05 = 3.0 m³
- 3Net Weight = 3.0 × 2,320 ÷ 1,000 = 6.96 t
- 4With 5% waste = 6.96 × 1.05 = 7.3 tonnes
Complete Worked Example: Parking Lot
| Parameter | Value |
|---|---|
| Length | 50 m |
| Width | 30 m |
| Thickness | 75 mm |
| Density | 2,320 kg/m³ |
| Waste | 5% |
Calculation:
- 1Area = 50 × 30 = 1,500 m²
- 2Volume = 1,500 × 0.075 = 112.5 m³
- 3Net Weight = 112.5 × 2,320 ÷ 1,000 = 261 t
- 4With waste = 261 × 1.05 = 274 tonnes
At 20 t per truck: 14 truckloads
Imperial Units Example
Driveway: 66 ft long, 10 ft wide, 2 inches thick
- 1Area = 66 × 10 = 660 ft²
- 2Volume = 660 × (2/12) = 110 ft³ = 110 ÷ 27 = 4.07 cubic yards
- 3Weight = 4.07 × 3,915 lbs/yd³ ÷ 2,000 = 7.97 short tons
(1 cubic yard HMA ≈ 145 lb/ft³ × 27 = 3,915 lb)
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Rather than doing this manually, use our free [Bitumen Calculator](/) or [Asphalt Calculator](/asphalt-calculator) to get instant results with material breakdown, truck load estimates, and cost calculation.
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