California Bearing Ratio (CBR)
Penetration test rating subgrade strength against crushed rock at 100. Soft clays run CBR 2–5, good granular subgrades 20+. Lower CBR demands thicker base and pavement layers — the soil under a driveway sets its design.
Where this appears in real estimates
This term isn't trivia — it's a working variable. These tools use it directly:
- pavement estimate tool — Multi-layer pavement takeoff: surface course, binder course and aggregate base tonnage in …
- sub-base estimate tool — Granular sub-base (GSB) tonnage for the layer between subgrade and base course.…
Go deeper
- Gravel vs Asphalt Driveway — head-to-head decision guide
- Concrete Slab or Shed Pad — full project walkthrough
- Fence in California — local pricing & climate
- Read the field guide on the blog — practitioner-level detail
- Related engineering article — from our licensed engineer
Reviewed: · Part of the CalculatorAsphalt Construction Glossary · Sources: see methodology & standards.