Engineering calculator
Rock Mass Rating (RMR) Calculator
Calculate the Rock Mass Rating (RMR) using Bieniawski 1989 classification scoring to assess rock quality for tunneling, mining, and excavation planning.
Result
Rock mass rating results
Your RMR evaluation will appear here
Select the rock parameters from the dropdowns, then click Calculate to determine the Rock Mass Rating.
Total RMR Score
/100 Basic parameter score
Orientation adjustment
Raw total
Class range
Scoring breakdown
Each selected parameter contributes points to the final RMR score.
RMR is an engineering classification aid. Use field data, project standards, and professional geotechnical review for design or safety decisions.
Guide
Rock Mass Rating Calculator Guide
Use this guide to understand what each RMR input means, how the point system is combined, and how to read the resulting rock mass class before using the estimate in a project workflow.
What is the Rock Mass Rating (RMR) System?
Rock Mass Rating is a geomechanical classification method used to describe the quality of a rock mass from field and laboratory observations. The system combines ratings for intact rock strength, RQD, discontinuity spacing, discontinuity condition, groundwater, and orientation adjustment.
The result is a score from 0 to 100 and a class from Class I to Class V. Higher scores indicate better rock mass quality, while lower scores suggest poorer conditions and a stronger need for engineering review, support design, and field verification.
The Six Parameters of RMR
The calculator uses dropdowns so each input maps directly to a rating value from the common Bieniawski 1989 table. The first five parameters build the basic score, then the orientation factor adjusts that score for the project geometry.
UCS
Uniaxial compressive strength rates the intact rock material before jointing effects are considered.
RQD
Rock Quality Designation estimates core quality from the percentage of sound core pieces.
Spacing
Discontinuity spacing describes how far apart major joints, bedding, or fractures are.
Condition
Discontinuity condition considers roughness, separation, weathering, continuity, and infill.
Groundwater
Dry, damp, wet, dripping, or flowing conditions change the rating because water can reduce stability.
Orientation
The adjustment accounts for whether discontinuities are favorable or unfavorable for the excavation.
Rock Mass Classes Explained
After the score is calculated, the RMR class gives a quick quality label. This label is useful for early comparison, but it should not replace detailed design checks or project-specific geotechnical judgment.
Very good rock mass quality with generally favorable engineering behavior.
Good rock mass quality, though jointing and groundwater should still be reviewed.
Fair rock mass quality where support and excavation conditions need careful review.
Poor rock mass quality that often requires stronger support and closer observation.
Very poor rock mass quality where specialist geotechnical review is especially important.
Example score 64/100 Basic score 69 pts Orientation -5 pts Class range 61 - 80
Example class
Class II - Good Rock This sample uses moderate-to-good rock quality values with a fair orientation adjustment.How to Use This Calculator
- 1Select UCS
Choose the compressive strength range from lab data, field estimates, or project records.
- 2Add RQD and spacing
Select the RQD percentage and the average spacing of discontinuities.
- 3Describe discontinuity condition
Match roughness, separation, weathering, continuity, and infill to the closest dropdown option.
- 4Choose groundwater and orientation
Add water conditions and the orientation adjustment for the excavation or opening.
- 5Review the RMR class
Use the score, class, and breakdown as an estimate that should be checked against project standards.
Applications in Tunneling and Mining
RMR is often used during tunneling, underground mining, excavation planning, and preliminary rock engineering review. It helps summarize several observations into one score so teams can compare rock mass quality across stations, boreholes, or project zones.
Because field conditions can change quickly, the RMR score should be treated as part of a broader assessment. Support recommendations, excavation method, groundwater control, slope behavior, and safety decisions should be reviewed by qualified professionals using full project data.
FAQ
Frequently Asked Questions
Clear answers about RMR, RQD, discontinuity orientation, and rock mass classification.
What is the difference between RMR and the Q-system?
RMR and the Q-system are both rock mass classification methods, but they use different input parameters, scoring ranges, and support recommendations. RMR uses additive ratings for strength, RQD, discontinuities, groundwater, and orientation, while the Q-system uses ratios based on joint sets, roughness, alteration, water, and stress reduction factors.
How is Rock Quality Designation (RQD) measured?
RQD is commonly measured from drill core by summing the lengths of sound core pieces longer than 10 cm, dividing by the total core run length, and converting the result to a percentage.
Why do we apply an adjustment for discontinuity orientation?
The same rock mass can behave differently depending on how joints, bedding, or fractures align with a tunnel, excavation, slope, or opening. The orientation adjustment accounts for whether those discontinuities are favorable or unfavorable for the project geometry.
Can RMR be used for slope stability analysis?
RMR can provide useful rock mass context for slopes, but slope stability often needs more detailed analysis of discontinuity orientation, groundwater, geometry, shear strength, seismic effects, and project-specific safety factors.
Who created the Rock Mass Rating system?
The Rock Mass Rating system was developed by Z. T. Bieniawski and is widely associated with the 1989 geomechanical classification approach used in tunneling, mining, and rock engineering.