Stope Volume Calculator
The calculator treats the stope as a regular rectangular prism and multiplies its three dimensions: Volume = strike length × width × height.
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Before you rely on this: First-pass guide only. Verify safety-critical or regulated work against the relevant standards, your project requirements and a qualified professional.
How to use this calculator
- Enter the stope's strike length, width and height in metres to get the prismatic block volume in cubic metres.
- Optionally add the ore bulk density (t/m³) to convert the volume into in-situ tonnes.
- Treat the result as an idealised rectangular block — apply your own dilution, overbreak and mining-recovery factors before quoting a reserve.
How it works
The calculator treats the stope as a regular rectangular prism and multiplies its three dimensions: Volume = strike length × width × height. The result is in cubic metres (m³) as long as every dimension is entered in metres.
If a bulk density is supplied, in-situ tonnage is Volume × bulk density, with density in tonnes per cubic metre (t/m³). Typical hard-rock ore is around 2.7–3.4 t/m³. This gives the geometric in-situ tonnes only — it does not account for stope taper, overbreak/underbreak, dilution from waste, or mining recovery, all of which must be layered on separately.
Worked example
Open stope tonnage from block dimensions. A sublevel open stope is 30 m along strike, 8 m wide and 20 m high. Volume = 30 × 8 × 20 = 4,800 m³. At a bulk density of 2.9 t/m³, in-situ tonnes = 4,800 × 2.9 = 13,920 t. This is a first-pass geometric estimate before dilution and recovery factors are applied.
Common mistakes
- Mixing units — entering width in metres but height in centimetres. Every dimension must be in metres for the volume to be correct.
- Treating the prismatic result as a final reserve. It ignores dilution, overbreak and recovery, so the mined tonnes will differ from this geometric figure.
- Using an in-situ (solid rock) density when you actually want broken/muck tonnes, or vice versa — the two densities differ because of swell, so pick the one that matches your purpose.
Frequently asked questions
Does this calculate solid or broken tonnes?
It gives in-situ (solid rock) tonnes when you use an in-situ bulk density. Once the ore is blasted it bulks up (swell), so broken/muck tonnes occupy more volume at a lower loose density — use your loose density if you want broken tonnage.
My stope isn't a neat rectangular box — is this still useful?
Yes, as a quick first-pass estimate. Real stopes taper, follow the ore lens and overbreak, so this prismatic figure is an approximation. For a reserve you should use a survey wireframe or block-model volume and apply dilution and recovery factors.
What bulk density should I use?
Use the site-specific measured density for your ore. As a rough guide, many hard-rock sulphide and base-metal ores fall around 2.7–3.4 t/m³, but this varies widely with mineralogy — always prefer your own assay/density data.
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