The true cost of an ERP implementation.

How this works

The calculator multiplies four things to estimate the cost your business absorbs internally during the implementation:

• Internal labor. Team size × loaded salary × percent of time × adjusted project duration (overrun factor applied).
• Opportunity cost. The same hours, multiplied by what those people would have generated if they were doing their day jobs instead. Defaults to 1.0x their loaded cost.
• Vendor quote. Pass-through from the input.
• Estimated true cost. Vendor quote + internal labor + opportunity cost.

The math is intentionally simple. Pricing your own internal time precisely is a fool’s errand at the business case stage. The point isn’t to land on a number to the dollar. The point is to land on a magnitude that includes the hidden costs, so your business case doesn’t pretend they aren’t there.

What it doesn’t capture

This calculator is a starting framework, not a complete TCO model. Things it does not include:

• Integration cost. The middleware, mapping, and engineering work to connect the new ERP to the surrounding stack. See The Integration Tax.
• Customization debt. Custom code piles up during implementation and shows up as maintenance cost forever after.
• Post-go-live adoption. Months 1 to 6 after launch are where workarounds calcify and trust in the system gets built or broken. See The Post-Go-Live Cliff.
• Productivity loss during cutover. The two to six weeks around go-live when nobody is fully productive in the new system or the old one.
• Change management and training. Often line-item-skipped by vendors. Lands on you.

If any of these matter in your situation, treat this number as a floor, not a ceiling.

What to do with the number

Compare it against the benefit case your business case projects. If the true cost is materially larger than the vendor quote you took to the board, and the benefit case wasn’t scaled accordingly, the ROI math is optimistic. Two practical next steps:

• Re-run the business case using the true-cost figure instead of the vendor quote. The result may still pencil out. Or it may suggest a different implementation strategy (phased rollout, different scope, different partner) before signing.
• Reserve a contingency sized to the hidden cost (internal labor + opportunity cost) and call it out as an explicit line item, not buried in the project budget. Your board would rather see a real number than a surprise.

For more on the patterns behind these numbers, read What ERP vendors don’t tell you about the true cost of implementation.