What is a good RMR score?

Scores of 81–100 (Class I) indicate very good rock. Scores of 61–80 (Class II) are good rock. Scores of 41–60 (Class III) are fair and require systematic support. Scores below 40 (Classes IV and V) represent poor to very poor rock requiring heavy, immediate support.

What is the difference between RMR76 and RMR89?

RMR89 (Bieniawski 1989) is the current industry standard. It has revised ratings for UCS and RQD, expands discontinuity condition into five sub-parameters, and updates the groundwater rating scale. Always use the 1989 version unless a project specifically requires the earlier edition.

How does RMR relate to the Q-System?

Both are empirical rock classification tools. The common correlation is: RMR ≈ 9 × ln(Q) + 44. On important projects, calculate both independently and compare. Significant divergence signals unusual site conditions worth investigating further.

How do I calculate RQD without core drilling?

Use Palmstrom's formula: RQD = 115 − 3.3 × Jv, where Jv is the number of joints per cubic meter. Alternatively use Priest and Hudson (1976): RQD = 100 × e^(−0.1λ) × (0.1λ + 1), where λ is mean joint frequency per meter.

Is this RMR calculator suitable for professional reports?

This calculator correctly implements Bieniawski 1989 and supports professional work as a computation aid. All input parameters must be assessed by a qualified geotechnical or mining engineer from actual field investigations and lab tests before use in final design.

About Us – Rock Mass Rating Calculator

About

About Rock Mass Rating Calculator

A free, accurate, and professional tool built to help geotechnical engineers, mining professionals, and geology students calculate Rock Mass Rating (RMR) using the Bieniawski 1989 classification system.

Our Mission

Rock mass classification should be accessible to every engineer — whether you're on a job site in Nevada, studying for your PE exam in Texas, or designing tunnel support systems for a major infrastructure project. We built this tool to eliminate the need for expensive software just to run a standard RMR calculation.

What We Offer

RMR Parameters

Rock Classes

100%

Free to Use

1989

Bieniawski Standard

All calculations follow the Bieniawski (1989) Engineering Rock Mass Classifications standard — the most widely accepted RMR methodology in the United States and globally.

What is Rock Mass Rating (RMR)?

Rock Mass Rating is a geomechanics classification system developed by Z.T. Bieniawski, first published in 1973 and revised in 1989. It provides a numerical score from 0 to 100 that describes the overall quality of a rock mass based on six key parameters:

Uniaxial Compressive Strength (UCS) of intact rock
Rock Quality Designation (RQD) — fracture frequency in core samples
Spacing of discontinuities — distance between joints and bedding planes
Condition of discontinuities — roughness, aperture, infill, and weathering
Groundwater conditions — dry to flowing
Orientation of discontinuities — favorable to very unfavorable

RMR is a standard requirement in Geotechnical Baseline Reports (GBRs) for major US tunneling and underground construction projects, and is routinely used by FHWA, USACE, and state DOTs nationwide.

Features of Our Calculator

Bieniawski 1989 Compliant

Fully implements the 1989 revision including all 5 discontinuity sub-parameters and application-specific orientation adjustments

Three application types

Orientation adjustment for Tunnel/Mine, Foundation, and Slope — each with correct Bieniawski penalty values

Instant results

Rock class, stand-up time, cohesion, friction angle, and support recommendations update in real time

PDF report download

Generate a formatted report with all parameters and results — ready to attach to field notes or project files

No registration

No account, no email, no paywall. Open the page, enter your data, get your answer

Saves your data

Your last entered values are saved in your browser so you can return and continue without re-entering everything

Who Uses This Tool

Our calculator is designed for professionals and students working in geotechnical, mining, and civil engineering fields:

Geotechnical Engineers

Site investigation, tunnel feasibility, and rock support design

Mining Engineers

Underground mine planning and stope stability assessment

Civil Engineers

Foundation design and slope stability for infrastructure projects

Geology Students

Learning and practicing rock mass classification for exams and coursework

PE Exam Candidates

Quick reference and calculation practice for the PE Geotechnical exam

Field Geologists

On-site classification during drilling programs and core logging

References and Standards

This tool is built strictly on peer-reviewed and industry-standard references:

Bieniawski, Z.T. (1989). Engineering Rock Mass Classifications. Wiley-Interscience, New York.
Bieniawski, Z.T. (1973). Engineering classification of jointed rock masses. Trans. South African Inst. Civ. Eng., 15, 335–344.
Deere, D.U. (1963). Technical description of rock cores for engineering purposes. Rock Mechanics and Engineering Geology, 1(1), 16–22. (RQD method)
Barton, N., Lien, R., and Lunde, J. (1974). Engineering classification of rock masses for the design of tunnel support. Rock Mechanics, 6, 189–236. (Q-System)
FHWA (2009). Rock Tunneling Reference Manual. US Federal Highway Administration.

Important Disclaimer

This calculator is provided for educational and preliminary engineering purposes only. Results should not be used as the sole basis for final design decisions, construction plans, or safety-critical applications. All geotechnical assessments must be reviewed and verified by a licensed Professional Engineer (PE) with relevant rock mechanics experience. Input parameters must be determined through proper field investigation and laboratory testing — not estimated without site data.