Free Web Tool

CBR Calculator

California Bearing Ratio (CBR) calculation for laboratory loads at 2.5 / 5.0 mm or direct field readings, with subgrade rating.

Inputs

Method (ASTM D1883)
  • CBR @ 2.5 = (P/13.24)·100, CBR @ 5.0 = (P/19.96)·100 (loads in kN; standard test).
  • Reported CBR = larger of the two penetration values (typically 2.5 mm).
  • Subgrade rating: <3 very poor, 3–7 poor-fair, 7–20 fair-good, 20–50 good-excellent.

Results

CBR @ 2.5 mm
CBR @ 5.0 mm
Reported CBR
Rating