ToolnozaStart with four separate production measures
Drilling metres, rock tonnes, productive hours, and specific drilling answer different questions. Total drilled metres measures the drilling completed. Tonnage estimates the rock volume represented by a surveyed excavation. Productive hours record time actively spent drilling under a defined shift rule. Specific drilling relates drilled metres to a measured rock quantity or volume using a clearly stated unit convention.
Keep these quantities separate in the report. A high drilled-metre total does not automatically mean a high tonnage or a successful blast. Production data should be tied to a defined workplace, shift, date range, and survey boundary.
Calculate drilled metres
For a simple round, total drilled metres = hole count × average actual drilled length, if every hole has the same length. For mixed holes, sum each measured length: M = L₁ + L₂ + … + Lₙ. Use actual drilled length from the drilling record, not just the planned collar-to-toe distance when deviation or incomplete holes matter.
Example: 20 holes averaging 10 m give 200 drilled metres. If four holes are 8 m and six are 11 m, those ten holes total 4 × 8 + 6 × 11 = 98 m. Record re-drills and abandoned holes under the site’s reporting convention so that productivity comparisons remain consistent.
Estimate surveyed rock tonnes
Tonnage = surveyed volume × in-situ density. If a measured excavation volume is 1,000 m³ and the selected in-situ density is 2.7 t/m³, estimated tonnage is 2,700 t. Use a survey-derived volume for the correct period and a density source appropriate to the rock mass. Do not substitute loose muck density without converting for swell and the reporting basis.
Survey boundaries, dilution, overbreak, underbreak, voids, and density variation can affect the result. Where density is not measured, label the value as an assumption and state who supplied it. Do not present estimated tonnes with false precision.
Calculate productive drilling hours and rates
Productive penetration rate = actual drilled metres ÷ productive drilling hours. If a machine drilled 200 m during 5 productive hours, the rate is 40 m/h. This measure excludes time categories outside the chosen productive definition, such as travel, setup, maintenance, and delays. Total shift availability or utilization should be reported separately.
Use the same time-code rules between periods and crews. A rate may rise because of changed rock conditions, hole length, bit type, operator practice, maintenance, or the way non-drilling time is classified. The metric helps describe performance; it does not establish the cause of a change.
Interpret specific drilling with a stated denominator
Specific drilling is often reported as metres drilled per unit of rock volume or tonnage. A volume-based measure could be 200 m ÷ 1,000 m³ = 0.20 m/m³. A mass-based measure could be 200 m ÷ 2,700 t = 0.074 m/t. These are different denominators and should not be compared as though they were the same KPI.
For comparison between headings, document the denominator, hole pattern, rock type, development geometry, and whether the metres include perimeter, lifter, or re-drilled holes. A single ratio cannot assess fragmentation, dilution, overbreak, advance per round, or downstream loading performance.
Use the production calculator and validate the data
- Enter the measured hole count and actual average length, or calculate a defensible average from the drilling log.
- Enter surveyed volume, in-situ density, productive penetration rate, and productive hours using the units displayed.
- Check that the period and workplace match across drilling logs, survey records, and time reports; label every assumed value.
Toolnoza’s Drill & Blast Calculator summarizes production quantities and rates. It does not design a blast, choose explosive charges, set initiation timing, or replace site procedures and authorized engineering review.
Frequently asked questions
Can I calculate tonnes from drilled metres alone? No. You need a surveyed volume or another documented geometric basis and an appropriate density.
Is productive penetration rate the same as shift productivity? No. It excludes non-drilling time under its definition; shift productivity should include the full time boundary you choose.
Can specific drilling compare different rock types? It can be one consistent KPI, but geology, geometry, pattern design, and reporting rules must be considered.
Does this tool create a blast design? No. It calculates production-reporting metrics only.
Related tools and sources
Use a measured survey and site-approved density values as primary inputs. For production systems, see the International Society of Explosives Engineers at https://isee.org/ and applicable mine regulations and operating standards for your jurisdiction. Related Toolnoza calculators are linked below.