ToolsRock MechanicsRock Strength Testing

Rock Weathering Grade Classifier

Classify rock weathering grade from Grade I (Fresh) to Grade VI (Residual Soil) per BS 5930 and BS EN ISO 14689. Interactive reference with descriptions and key characteristics.

Last updated 26 May 2026

About this tool

Interactive reference for rock weathering grades I–VI per BS 5930:2015 and BS EN ISO 14689. Select a grade to see the full description and key characteristics for field identification.

Weathering grade is a fundamental part of every rock description and directly affects engineering parameters. This tool provides the standard definitions in a quick-reference format for use in the field or when reviewing core logs.

How to use this tool

1. Select the weathering grade — based on your field observations of discolouration, decomposition, and strength.

2. Review the description — check it matches what you see in the exposure or core.

Technical information

Grades I–VI follow BS 5930:2015 and BS EN ISO 14689. For heterogeneous rock masses, describe the proportions of each grade present (e.g. 'Grade II to IV, predominantly III').

Limitations

This is a reference tool, not a calculator. Weathering grade assignment requires field judgement and experience.

The six-grade scale is a simplification. Some rock types (e.g. granite, tropical residual soils) may benefit from sub-grading or material-specific scales.

Revision history

26 May 2026: Initial release

Disclaimer

This tool is provided for educational and general information purposes only. It is not a substitute for professional engineering advice, design or verification.

Diggy and its contributors are not licensed engineering consultants and no results generated by this tool should be used directly for construction, design or safety-critical decisions.

All values and outputs are based on published empirical correlations and should be independently checked and confirmed by a qualified geotechnical engineer before use.

By using this tool, you accept full responsibility for how you interpret and apply the information provided.

Spotted an error? Let us know.

Select weathering grade

Related tools

Compressive Strength CalculatorCalculate compressive strength from failure load and specimen dimensions. Supports cubes, cylinders, and cores with cylinder-to-cube conversion. Includes BS EN ISO 14689 rock strength classification.Point Load to UCS ConverterConvert point load index Is(50) to uniaxial compressive strength using size-corrected ISRM method. Supports diametral, axial, and irregular lump tests with rock-type-specific k factors.Rock Young's Modulus CalculatorEstimate intact and rock mass Young's modulus from UCS and RQD using Deere modulus ratios, Rowe & Armitage, and Zhang & Einstein correlations.Schmidt Hammer to UCSEstimate rock UCS from Schmidt hammer rebound number using three correlations: Miller (1965), Aufmuth (1973), and Katz et al (2000). Includes orientation correction.Sonic UCS EstimatorEstimate rock UCS from P-wave velocity using three correlations. Enter velocity directly or from path length and transit time. Includes UPV quality grading per BS EN 12504-4.