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RQD / Core Recovery Calculator

Q: "What is RQD?"

"RQD stands for Rock Quality Designation. It is the sum of core piece lengths longer than the cutoff, divided by the run length."

Q: "Can I enter from/to depths and run length at the same time?"

"Yes. If both are entered, the tool warns you when the run length and the from/to difference do not line up closely enough."

Q: "Can I mix units in the core piece list?"

"Yes. You can mix unit-tagged values. If a value has no unit, it is interpreted using the current piece unit."

Q: "Does it support decimal commas?"

"Yes. Inputs such as 1,25 are accepted."

Q: "Can RQD exceed 100%?"

"Normally no. If it does, check for unit mistakes or duplicated input."

Review interval-by-interval core length, recovered length, RQD, core recovery, and core loss in one place.

It supports both from/to interval entry and direct core piece lengths, with units and decimal places controlled from Settings.

Samples

Sound core interval

Input Run length 1.00 m, core pieces 32 cm / 28 cm / 22 cm / 18 cm

Output RQD 100.0%, core recovery 100.0%, quality class Excellent

Fractured interval

Input Run length 1.00 m, core pieces 18 cm / 14 cm / 9 cm / 8 cm / 7 cm / 6 cm / 5 cm / 4 cm

Output RQD 32.0%, core recovery 71.0%, quality class Poor, fracture zone flagged

Low-recovery long run

Input Run length 10 ft, core pieces 18 in / 12 in / 8 in

Output RQD 31.7%, core recovery 31.7%, loss flag shown

Frequently asked questions

What is RQD?

RQD stands for Rock Quality Designation. It is the sum of core piece lengths longer than the cutoff, divided by the run length.

Can I enter from/to depths and run length at the same time?

Yes. If both are entered, the tool warns you when the run length and the from/to difference do not line up closely enough.

Can I mix units in the core piece list?

Yes. You can mix unit-tagged values. If a value has no unit, it is interpreted using the current piece unit.

Does it support decimal commas?

Yes. Inputs such as 1,25 are accepted.

Can RQD exceed 100%?

Normally no. If it does, check for unit mistakes or duplicated input.

Glossary

RQD

The sum of core piece lengths longer than the cutoff, divided by the run length.

Core recovery

The total recovered core length divided by the run length.

Run length

The total length of the drill interval.

Core piece length

The length of each recovered core fragment.

Cutoff length

The minimum piece length counted toward RQD.

Formulas

map[Text:recovery = recovered_length / run_length × 100 text:recovery = recovered_length / run_length × 100]
map[Text:rqd = sum(piece_length >= cutoff_length) / run_length × 100 text:rqd = sum(piece_length >= cutoff_length) / run_length × 100]
map[Text:core_loss = max(run_length - recovered_length, 0) text:core_loss = max(run_length - recovered_length, 0)]
map[Text:quality_class = RQD-based classification text:quality_class = RQD-based classification]
map[Text:fracture_flag = RQD < threshold or quality class is Poor/Very poor text:fracture_flag = RQD < threshold or quality class is Poor/Very poor]
map[Text:loss_flag = core recovery < threshold text:loss_flag = core recovery < threshold]

Notes

This tool is a screening aid, not a replacement for geologic interpretation or mine planning.
If you enter both from/to depths and run length, always check unit consistency.
Tune the cutoff length and thresholds to your site standards.
If a result exceeds 100%, suspect a unit mistake or duplicated input.

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