About This RMR Calculator
What This Tool Is
The Rock Mass Rating Calculator is a free, browser-based geotechnical tool that implements the Bieniawski 1989 Rock Mass Rating classification system. It allows engineers, researchers, and students to input six standard rock mass parameters and receive an instant numerical rating, rock class designation, estimated stand-up time, and preliminary support recommendations.
The calculator was designed to streamline the RMR assessment process that is traditionally performed by hand using lookup tables. Rather than flipping through reference charts, users select values from clearly labelled dropdown menus and receive results immediately. All calculations happen in the browser, so no data is transmitted to any server.
Technical Basis and Accuracy
Every rating value, class boundary, stand-up time estimate, and support recommendation in this tool is drawn directly from the tables published by Professor Z.T. Bieniawski in his 1989 monograph Engineering Rock Mass Classifications. The six parameters assessed are:
- Uniaxial compressive strength of intact rock material
- Rock Quality Designation (RQD)
- Spacing of discontinuities
- Condition of discontinuities (persistence, aperture, roughness, infilling, and weathering)
- Groundwater conditions
- Orientation of discontinuities (adjustment for tunnels, foundations, or slopes)
The rating intervals, class boundaries (I through V), and support guidelines follow the 1989 revision precisely. This version is the most widely cited edition in geotechnical practice and remains the standard reference in numerous international design codes and project specifications.
Who This Tool Is For
The RMR Calculator is built for a broad range of professionals and learners in the geosciences and civil engineering fields:
- Geotechnical engineers who need a quick preliminary classification during site investigations, feasibility studies, or design phases for tunnels, slopes, and foundations.
- Mining engineers assessing rock mass quality for underground excavation planning, pillar design, and ground support selection in mining operations.
- Geology students studying rock mechanics and engineering geology courses who want a hands-on tool to practice RMR classification alongside textbook examples.
- Civil engineers working on infrastructure projects that require rock mass characterisation for dam foundations, road cuts, bridge abutments, and retaining structures.
- Tunnelling consultants preparing preliminary assessments and comparing RMR-based support recommendations with other classification systems such as the Q-system.
Commitment to Free Access
This calculator is and will remain completely free to use. There are no premium tiers, no registration requirements, and no paywalls. The tool runs entirely in your browser using HTML, CSS, and JavaScript. We believe that fundamental geotechnical reference tools should be accessible to every engineer and student regardless of budget or institutional affiliation.
We do not collect personal data through the calculator itself. The only external service is Google Analytics, which helps us understand general usage patterns so we can improve the tool. You can read more about our data practices on the Privacy Policy page.
Important Disclaimer
This calculator is intended for preliminary assessment and educational purposes only. It is not a substitute for professional site investigation, detailed geotechnical analysis, or engineering judgement by a qualified professional. Rock mass classification is inherently dependent on the quality and representativeness of input data, which requires direct observation and measurement by experienced personnel.
Real-world rock masses are complex, heterogeneous, and anisotropic. A single RMR value cannot capture all the variability present at a site. Users should always supplement classification results with additional investigation methods, laboratory testing, and numerical modelling as appropriate for the scale and risk profile of their project.
The authors and operators of this website accept no liability for any decisions, designs, or outcomes based on the results produced by this tool. All engineering decisions should be reviewed and approved by a licensed geotechnical professional.