Calculator Inputs
Use consistent metric units throughout the calculation.
Example Data Table
This sample row shows how the calculator can be used in a practical bench planning case.
| Project | Pattern | Length (m) | Width (m) | Bench (m) | Burden (m) | Spacing (m) | Hole Dia (mm) | Rounds | Final Holes | Total Drilling (m) | Total Explosive (kg) |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Example Quarry Cut | Staggered | 42.00 | 27.00 | 10.00 | 3.20 | 3.80 | 127 | 3 | 115 | 1,311.00 | 13,236.34 |
Formula Used
Blast Area = Blast Length × Blast Width
Effective Area per Hole = Burden × Spacing × Pattern Factor
Pattern Factor = 1.000 for rectangular, 0.866 for staggered
Usable Area = Blast Area × (Utilization Factor ÷ 100)
Area-Based Holes = Ceiling(Usable Area ÷ Effective Area per Hole)
Rows = Ceiling(Blast Width ÷ Burden)
Holes per Row = Ceiling(Blast Length ÷ Spacing)
Grid Holes = Rows × Holes per Row
Recommended Holes = Ceiling(Max(Area-Based Holes, Grid Holes) × (1 + Extra Hole Allowance ÷ 100))
Hole Length = Bench Height + Subdrill
Charge Length = Max(0, Hole Length - Stemming - Deck Length)
Explosive per Hole = Charge Length × π × (Hole Diameter ÷ 2000)² × Explosive Density
Total Drilling = Recommended Holes × Hole Length
Total Explosive = Recommended Holes × Explosive per Hole
Powder Factor = Total Explosive ÷ Blast Volume
How to Use This Calculator
- Enter the blast length and width for the area you plan to shoot.
- Choose the drilling pattern, then enter burden and spacing values.
- Add bench height, subdrill, stemming, and deck length for the hole profile.
- Provide hole diameter and explosive density to estimate charge mass.
- Set the utilization factor to reflect usable area after edge loss or field constraints.
- Add an extra hole allowance if you want contingency for collar adjustments or irregular ground.
- Enter the number of rounds to estimate project totals.
- Press the calculate button to show results above the form, review the chart, and export the summary to CSV or PDF.
FAQs
1) What does this calculator estimate?
It estimates hole count, rows, holes per row, drilling length, charge length, explosive mass, and project totals from your layout inputs. It is useful for early planning, budgeting, and comparing pattern options before detailed field design.
2) Why are both area-based and grid-based holes shown?
Area-based holes come from theoretical coverage. Grid-based holes come from practical row and column spacing. Using the larger value helps avoid undercounting when a workable field layout needs more holes than simple coverage math suggests.
3) What is burden in blast planning?
Burden is the distance from a hole to the free face or the next row. It strongly affects fragmentation, throw, breakage at the toe, and the number of rows required in a layout.
4) What changes when I select a staggered pattern?
Staggered layouts improve coverage efficiency. The calculator uses a 0.866 factor for triangular spacing, which means each hole represents area differently than a rectangular pattern during the theoretical coverage check.
5) Why is subdrill added to hole length?
Subdrill extends the hole below floor level so the bench breaks cleanly at the toe. It increases total drilling metres and can also increase charge length when stemming and deck values remain unchanged.
6) Does hole diameter change the number of holes?
Hole diameter does not directly set the hole count here. It mainly changes explosive mass because larger holes hold more charge per metre. Count is driven by area, burden, spacing, and contingency.
7) Should blast hole quantity always be rounded up?
Yes, planning normally rounds up because partial holes are not practical. Final field design may still shift collar positions, trim rows, or edge holes after geology and site conditions are reviewed.
8) Can this calculator replace an engineered blast design?
No. Use it for estimating and option comparison only. Final blasting plans should also consider geology, timing, explosive selection, regulations, vibration limits, and site safety requirements.