How to Calculate Asphalt — Formulas, Units & Worked Examples
Calculating asphalt tonnage uses the same four-step formula whether you're estimating a 500 sq ft driveway or a 5-mile highway project.
Step 1 — Find the Volume
Volume (ft³) = Length (ft) × Width (ft) × (Thickness in ÷ 12)
Example: 40 ft × 12 ft, 2 in thick → 40 × 12 × (2/12) = 80 ft³
Step 2 — Convert to Weight
Weight (lbs) = Volume × 145
Example: 80 × 145 = 11,600 lbs
Step 3 — Convert to Tons
US short tons = lbs ÷ 2,000
Example: 11,600 ÷ 2,000 = 5.8 tons
Step 4 — Add the 10% Waste Buffer
5.8 × 1.10 = 6.4 tons to order
Worked Example: 1,000 sq ft Driveway at 2.5 Inches
- Volume: 50 × 20 × (2.5/12) = 208.3 ft³
- Weight: 208.3 × 145 = 30,208 lbs
- Tons: 30,208 ÷ 2,000 = 15.1 tons
- With buffer: 15.1 × 1.10 = 16.6 tons to order
Common Mistakes
- Not converting inches to feet (2 inches = 0.167 ft, not 2 ft).
- Mixing imperial and metric.
- Skipping the 10% buffer and under-ordering.
Skip the Math
Use the main asphalt calculator to get instant results.