Tarmac & Asphalt Calculator
About This Calculator
This tarmac calculator helps you determine the quantity of asphalt or tarmac needed for your driveway, path, or road project. Tarmac is typically ordered by the tonne, so this calculator converts your area and depth measurements into tonnes required.
The calculator accounts for different tarmac types (standard, porous, heavy-duty) and includes a wastage allowance for accurate ordering.
Tarmac Types
Standard Asphalt / Tarmac
The most common choice for domestic driveways and paths. Density: ~2,400 kg/m³
Porous / Permeable Tarmac
Allows water to drain through, complying with SUDS regulations. Lighter density: ~2,000 kg/m³
Heavy-Duty Commercial Grade
For roads, car parks, and high-traffic areas. Density: ~2,500 kg/m³
Recommended Thickness
| Application | Min. Thickness | Notes |
|---|---|---|
| Paths / Patios | 25-40mm | Light foot traffic only |
| Domestic Driveways | 50-60mm | Standard car traffic |
| Heavy Driveways | 60-75mm | Vans, multiple vehicles |
| Car Parks | 75-100mm | Commercial use |
| Roads | 100mm+ | With proper sub-base |
Example Calculations
Standard Driveway
A driveway 10m × 4m at 50mm thickness:
- Area: 40 m²
- Volume: 2.0 m³
- Tarmac required: ~5.0 tonnes
- With 5% wastage: 5.3 tonnes
Porous Driveway (SUDS)
A driveway 8m × 3m at 60mm thickness:
- Area: 24 m²
- Volume: 1.44 m³
- Porous tarmac: ~2.9 tonnes
Commercial Car Park
A parking area 20m × 10m at 80mm thickness:
- Area: 200 m²
- Volume: 16.0 m³
- Heavy-duty tarmac: ~40 tonnes
Important Notes
- Tarmac must be laid on a properly prepared sub-base (typically MOT Type 1)
- Order 5-10% extra to account for wastage, edges, and irregularities
- Tarmac cools quickly — ensure your contractor has adequate labour and equipment
- Porous tarmac requires special base preparation for drainage
- Minimum order quantities may apply (typically 1-2 tonnes)
Ready to Calculate?
Enter your dimensions and get instant tarmac quantity calculations.
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References & Sources
Standards Cited
- BS 594987 — Asphalt for roads and other paved areas — Specification for transport, laying, compaction and type testing protocols
Defines asphalt densities, laying depths, and specification for driveways and road surfaces - DMRB CD 226 — Highways England Design Manual for Roads and Bridges — Pavement design
Design guidance for pavement layer thicknesses and material specifications for roads View →
Formulas Used
- Tarmac volume:
volumeM3 = length x width x (depth / 1000)
Source: Basic geometry - Tonnes required:
tonnesRequired = volumeM3 x density / 1000
Source: BS 594987 — Densities: standard 2400, porous 2000, heavy-duty 2500 kg/m3 - Coverage per tonne:
coverageM2 = (tonnes x 1000 / density) / (depthMm / 1000)
Source: BS 594987
Key Assumptions
- Asphalt densities: standard 2400 kg/m3, porous/permeable 2000 kg/m3, heavy-duty 2500 kg/m3 — BS 594987
- Recommended depths: pathways 25-40mm, driveways (light) 50mm, driveways (heavy) 60-75mm, roads 75-100mm+ — DMRB CD 226 / BS 594987
- Typical wastage allowance of 5-10% — Industry standard practice