Estimate to Complete (ETC)

Estimate to Complete (ETC) is the expected cost of finishing all remaining work. It feeds directly into the Estimate at Completion: EAC = AC + ETC. ETC can be derived in two main ways. The formulaic approach uses EVM indices: ETC = (BAC − EV) ÷ CPI, which assumes the remaining work will be completed at the same efficiency as work to date. The bottom-up approach has the project team re-estimate the remaining work in detail — re-planning from the current position — and the sum of those estimates becomes ETC. The bottom-up approach is more work but more accurate when the project's circumstances have changed materially.

The choice between formulaic and bottom-up ETC depends on project stage and circumstances. In early and mid-project, when circumstances are broadly as planned and CPI is stable, the formulaic approach provides a reliable and unbiased forecast. After a significant scope change, disruption event, or change in execution strategy, a bottom-up re-estimate is necessary because historical CPI no longer reflects the conditions under which the remaining work will be done. Using a formulaic ETC through a material disruption event will produce a systematically incorrect EAC.

ETC should be reviewed and challenged at every reporting cycle. A common governance failure is allowing ETC to decrease by exactly the amount spent in each period — effectively reporting spend without updating the forecast. This produces an EAC that does not change over time, which gives false comfort that the project is on track. A realistic ETC will fluctuate as scope crystallises, risks mature, and performance data accumulates. If ETC is moving perfectly smoothly with no variation, either the project is unusually well-controlled or the estimates are not being genuinely revisited.