Can this calculator choose a safe powder factor?

No. It only reports a ratio from quantities you enter. Geology, confinement, explosive properties, vibration, flyrock and local rules require a qualified blasting professional and site-specific controls.

What is the difference between kg/t and kg/m³ powder factor?

Powder factor expressed in kg/t (per tonne) accounts for rock density variation and is preferred for ore planning. Powder factor in kg/m³ (per cubic meter) is common in quarrying and civil excavation where volume is the billing unit. To convert: kg/m³ = kg/t × rock density (t/m³).

Does a larger powder-factor number guarantee finer fragmentation?

No. Powder factor is a reporting indicator, not a complete blast design. Rock structure, confinement, explosive energy, charge distribution, initiation and geometry also affect the result.

Why does my powder factor differ from the design value?

Actual powder factor can deviate from design due to misfires (unfired holes reduce total explosive mass), hole collapse reducing charge length, or inaccurate blast volume measurement. Always reconcile actual explosive loaded against the surveyed muck volume.

Can I use this tool for underground blasting?

You can use it to calculate an observed mass-per-tonne or mass-per-volume ratio from recorded quantities. Do not use it to select underground charge quantities or blast geometry.

Blast Powder Factor Calculator

Divide the actual explosive mass by the measured rock mass or blasted volume, then convert the result among kg/t, kg/m³, lb/short ton, and lb/yd³ when density is available.

Blast Parameters

Total Explosive Loaded (kg)

Rock Quantity Mode

Total Rock Mass (tonnes)

Rock Density (t/m³) — for cross-unit conversion

Granite ≈ 2.6–2.7 | Limestone ≈ 2.3–2.7 | Basalt ≈ 2.8–3.1

Optional comparison target (kg/t)

Used only to show variance from a target supplied by your approved plan.

Results

Enter blast parameters and click Calculate.

Reporting scope and safety

Use actual explosive mass and surveyed blasted volume or measured tonnage. Do not infer a charge from a generic range: powder factor varies with geology, confinement, explosive properties and blast geometry. Blast design must be performed and approved by qualified personnel under applicable law.

Definitions: USACE EM 1110-2-3800. Safety context: NIOSH blasting and explosives.

Summary

Divide the actual explosive mass by the measured rock mass or blasted volume, then convert the result among kg/t, kg/m³, lb/short ton, and lb/yd³ when density is available.

How it works

Enter the total mass of explosive loaded in the blast (kg).
Choose whether to calculate per tonne of rock or per cubic meter.
For the per-tonne mode, enter the total rock mass (tonnes); for per-volume mode, enter the total blast volume (m³).
Optionally enter rock density to convert between tonne-based and volume-based results automatically.
The tool computes powder factor and displays equivalent values in both kg/t and kg/m³.

Use cases

Estimate explosive consumption for a production blast pattern in an open-pit mine.
Compare powder factors across blast rounds to identify fragmentation issues.
Benchmark blast efficiency against industry standards for a given rock type.
Convert between kg/t and kg/m³ powder factor when switching reporting units.
Validate drill-and-blast designs against target fragmentation requirements.
Calculate total explosive cost per tonne of ore or waste material.

Frequently Asked Questions

Last updated: 2026-09-20 · Reviewed by Nham Vu