To-Complete Performance Index (TCPI)

The To-Complete Performance Index (TCPI) answers a simple but powerful question: at what CPI does the remaining work need to be performed to hit a given cost target? If the target is the original BAC, the formula is TCPI = (BAC − EV) ÷ (BAC − AC). If the target is the current EAC, the formula is TCPI = (BAC − EV) ÷ (EAC − AC). A TCPI of 1.0 means the remaining work must be performed at exactly the same efficiency as budgeted — exactly to plan. A TCPI above 1.0 means the project needs to perform better than planned to hit the target. A TCPI significantly above 1.0 is a red flag: it means the budget target is effectively unachievable.

TCPI is most useful as a sanity check on overly optimistic EAC forecasts. If a project is running at CPI 0.85 and the project team is forecasting EAC = BAC (implying they will recover all the cost overrun in the remaining work), the TCPI calculation will show what CPI they need to achieve to make that forecast true. If the required TCPI is 1.30 — meaning they need to perform 30% better than planned for the rest of the project — that is not credible, and the EAC is almost certainly too low. TCPI serves as an independent check on the realism of any bottom-up ETC.

When TCPI relative to BAC and TCPI relative to EAC diverge significantly, that gap tells you how much the project has moved away from its original budget. A project where TCPI(BAC) = 1.5 and TCPI(EAC) = 1.0 has acknowledged in its EAC that it cannot recover the overrun, and the EAC is a realistic forecast — the remaining work only needs to be done at plan efficiency. A project where both values are 1.5 is either refusing to acknowledge the overrun in its EAC, or is expecting an extraordinary recovery. Neither situation ends well without intervention.