Compaction Lift Calculator

Why Lift Thickness Matters

Compaction works from the surface down. If a lift is too thick, the compactor's energy cannot reach the bottom of the layer — leaving loose, poorly-compacted material that will settle under load. Getting your lift thickness right is one of the most critical steps in earthwork quality control.

The 95% Proctor Standard

Most specs require 95% Standard Proctor (ASTM D698) or 98% Modified Proctor (ASTM D1557) for structural fills under roads, foundations, and embankments. Your lift thickness and pass count must be proven with field density testing (nuclear gauge or sand cone) — this calculator gives you a starting estimate, not a substitute for testing.

Padfoot vs. Smooth Drum

• Smooth drum vibratory: Best for granular materials — gravel, crushed stone, road base. The vibration densifies particle packing.
• Padfoot / Sheepsfoot: Best for cohesive soils — clay, silty clay. The feet penetrate and knead the material, breaking up clods and achieving density from the bottom up.
• Pneumatic tire: Good for mixed materials and asphalt base courses. Provides kneading action with some flexibility.

Typical Pass Counts

• Granular sub-base: 4–8 passes at 8–12" lift
• Clay fill: 6–10 passes at 6–8" lift
• Asphalt base: 4–6 passes with steel drum
• Always verify with field density tests — manufacturer specs and soil lab results override general estimates.