Cost per tonne is simple to define: the cost of mining or processing for a period divided by the tonnes for that period. Getting a number you trust each month is harder, because the costs sit in the ERP or accounts, the maintenance system, the fuel system and payroll, while the tonnes sit in production or weighbridge records. For gold producers, all-in sustaining cost (AISC) adds more lines and a reconciliation to the financial statements. In most small and mid-tier mines and quarries, both are built in Excel each month. This article explains why, and how to join the data so a mining dashboard shows cost per tonne by site, pit and month without the rebuild.
Why cost per tonne lives in Excel
The cost-per-tonne calculation itself is easy. The data behind it is not:
- Maintenance costs sit in the maintenance system (MEX, the ERP's plant module or similar), against work orders and equipment.
- Fuel is invoiced in the accounts as bulk deliveries, but issued to machines in a fuel system or on dockets.
- Payroll and contractor costs come from payroll, contractor invoices and timesheets, often coded by cost centre rather than by pit or activity.
- Production tonnes come from the production system, truck counts, surveys or the weighbridge, and often arrive a day or more after the costs.
Each system has its own codes for sites, equipment and periods. Someone exports from each, maps the codes by hand, adjusts for accruals and timing, and divides. It works, but it depends on one person, takes days after month end, and is hard to check. When the board or a lender asks why cost per tonne moved, the answer is in someone's workbook.
What a reliable cost per tonne needs
Common codes across systems
The most important step is agreeing how sites, pits, activities (mining, haulage, processing), equipment and periods line up across systems. Once that mapping exists in one place, every source can be joined to it. Without it, every month starts from scratch.
Costs that match the ledger
The total cost in the report should agree with the general ledger for the period. Maintenance, fuel and labour detail from the operating systems explains the cost. The ledger confirms it is complete, including accruals for contractor work and fuel not yet invoiced.
Tonnes from the right source
Decide which tonnes you divide by: mined, moved, processed or sold. The answer may differ by report. Once decided, the figure should come from one system, with surveys or reconciliations applied consistently.
A monthly view that anyone can read
With the data joined, a Power BI report over Xero or MYOB, or over your ERP, shows cost per tonne by site, pit, activity and month. You can click from a spike to the work orders, fuel or contractor invoices behind it. Our business intelligence page covers the wider reporting setup.
AISC for gold producers
All-in sustaining cost is a measure published by the World Gold Council, first issued in 2013 and updated in 2018. It aims to show the full cost of sustaining current production, not just site operating costs.
What AISC covers
In broad terms, the World Gold Council guidance includes site operating costs, sustaining capital, and the corporate general and administrative costs needed to support current operations, with by-product credits taken into account. It excludes items such as non-sustaining project costs at new operations or major projects, impairment, financing costs and interest, and most working capital movements. AISC is commonly reported per ounce. The guidance sets out the specific cost lines and how to treat items such as royalties, exploration and rehabilitation, so read it, and agree your definitions with your accountant and auditor, before building anything.
The reconciliation requirement
The World Gold Council guidance calls for a numerical reconciliation between the financial statement line items (under IFRS or US GAAP) and the costs included in AISC. That is a data problem as much as an accounting one. Splitting sustaining from growth capital, allocating corporate costs and matching it all to the statements requires costs coded consistently at the source. If capital spend is not tagged as sustaining or growth when it is approved, someone has to work it out later, every quarter.
Why it matters for listed producers
ASX-listed producers report production and costs in their quarterly activity reports, and many gold producers include AISC. A cost per ounce that is rebuilt in a spreadsheet each quarter is hard to keep consistent from one quarter to the next.
Do you need a project?
Not always. A single-pit operation with one ERP that already holds maintenance, fuel and payroll may get a good cost per tonne from the ERP's own reports. A mining-specific reconciliation suite may suit a large mid-tier miner. A connected reporting setup makes sense when the data sits across several systems, the spreadsheet depends on one person, and the suites are more than you need.
Frequently asked questions
How do you calculate cost per tonne in mining?
Divide the total cost for the period by the tonnes for the same period. The detail is in the definitions: which costs are included, which tonnes are used (mined, moved, processed or sold), and how timing and accruals are handled. Agree those first.
What is AISC?
All-in sustaining cost is a World Gold Council measure of the cost of sustaining current gold production, usually stated per ounce. It includes site operating costs, sustaining capital and corporate costs, and the guidance calls for a reconciliation to the financial statements.
Can a mining dashboard pull from our ERP and maintenance system?
Usually, yes. Most ERPs and maintenance systems can export data or be read directly. The work is in mapping codes so sites, equipment and periods line up, and in matching totals to the ledger.
Do we need to replace our ERP to get cost per tonne?
No. The aim is to join the systems you already have. Replacing an ERP is a much bigger decision and is rarely needed just for reporting.
How long does it take?
It depends on how many systems are involved and how clean the codes are. We scope every project first and give a fixed quote after a free initial chat.
If your cost per tonne is rebuilt in Excel each month, book a free initial chat. We'll look at where your costs and tonnes sit and tell you honestly whether a connected report is worth it. See also our mining services page.