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Core Recovery Calculator

Calculate Rock Quality Designation (RQD), Total Core Recovery (TCR) and Solid Core Recovery (SCR) for rock core logging.

Last updated 11 February 2026

About this tool

Calculate RQD (Rock Quality Designation), TCR (Total Core Recovery) and SCR (Solid Core Recovery) from your diamond drilling core runs.

This calculator helps geotechnical engineers and drillers assess rock mass quality and drilling performance from core logging data.

How to use this tool

Enter run length. Input the total length of the core run attempted (typically 1.5m or 3m).
Enter total core recovered. Input the total length of all recovered core pieces.
Enter solid core length. Input the sum of intact, unbroken core pieces.
Enter RQD pieces. Input the total length of core pieces that are 100mm or longer.

What is RQD?

Rock Quality Designation (RQD) is a modified core recovery percentage that quantifies rock mass quality. Only intact core pieces 100mm or longer are counted in the RQD measurement.

RQD was developed by D.U. Deere in 1964 and is a key parameter in rock mass classification systems like RMR and Q-system.

What is TCR and SCR?

Total Core Recovery (TCR) is the percentage of core recovered compared to the drilled length. It indicates drilling performance and potential core loss.

Solid Core Recovery (SCR) is the percentage of intact, unbroken core recovered. It provides an indication of rock quality and drilling disturbance.

Limitations

RQD is only valid for NX-size core or larger (minimum 54mm
diameter).
Natural fractures should be differentiated from mechanical
breaks caused by drilling.
RQD may not be representative for highly weathered or weak rock
masses.
Results should be used in conjunction with other geotechnical
parameters for rock mass classification.

Technical information

TCR (%): TCR = (Total Length of Core Recovered / Run Length) × 100

SCR (%): SCR = (Length of Solid Core / Run Length) × 100

RQD (%): RQD = (Sum of Core Pieces ≥100mm / Run Length) × 100

Rock Quality Classification:

< 25% = Very Poor | 25-50% = Poor | 50-75% = Fair | 75-90% = Good | ≥ 90% = Excellent

Revision history

11 February 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.

Run length (m)

Total length of core run attempted.

Total core recovered (m)

Total length of all recovered core pieces.

Solid core length (m)

Sum of intact, unbroken core pieces.

RQD pieces length (m)

Total length of core pieces ≥100mm.