Rock Mass Rating Calculator

How the Rock Mass Rating calculator works

Formula. Strength score is 15 above 250, 12 above 100, 7 above 50, otherwise 4. RQD score is 20 above 90, 17 above 75, 13 above 50, otherwise 8. Spacing score is 20 above 200, 15 above 60, 10 above 20, otherwise 5. RMR is the sum of those three scores.

Example. Strength 120 scores 12, RQD 80 scores 17, and spacing 100 scores 15. The total is 12 + 17 + 15 = 44.

Limitation. A full Rock Mass Rating also scores joint condition and groundwater. This page adds only strength, RQD, and spacing, so the total is not a complete RMR out of 100.