A project forecast predicts how a project will turn out financially, based on work already performed and work still remaining. Two values are central to that prediction: ETC (Estimate To Complete) and EAC (Estimate At Completion). When a snapshot brings actual project data into a forecast, the Snapshot Matching setting decides which of the two is recalculated: ETC Recalculated keeps EAC fixed and recalculates ETC, while EAC Recalculated keeps ETC fixed and recalculates EAC. This page explains what ETC and EAC represent, how Snapshot Matching applies that choice, and how to interpret the result, including a negative ETC.
Three related settings are involved: the ETC option chosen when a forecast version is created, the ongoing Snapshot Matching setting on the forecast, and, optionally, the EAC Workbench as a structured way to build EAC. Each is covered below.
ETC (Estimate To Complete) represents the cost, revenue, effort, or hours still needed to complete the remaining work on a project. It is entered and revised throughout project execution. Typical reasons to update ETC include:
| For cost: ETC = EAC – (Committed Cost + Used Cost) For revenue: ETC = EAC – (Preliminary Revenue + Posted Revenue) |
EAC (Estimate At Completion) represents the forecasted total outcome of the project once it is finished, combining what has actually happened on the project so far with the current estimate of what remains. Typical reasons to update EAC include:
| For cost: EAC = Committed Cost + ETC, where Committed Cost = Used Cost +
Committed Cost For revenue: EAC = Preliminary Revenue + Posted Revenue + ETC |
Because ETC and EAC are tied together by this relationship, a change to either value, or to the cost/revenue already incurred, affects the other. Which value stays fixed and which one moves is exactly what the Snapshot Matching setting decides. The EAC Workbench uses this same relationship with additional inputs, such as Estimated Future Commitment and connected contract change orders; see About EAC Workbench for those calculations.
A snapshot captures the project's status at a specific point in time, known as the Cut-Off Date. It can include estimated, planned, and incurred cost and revenue, reported hours, progress information, and the connected objects that generated them. Connecting a snapshot to a forecast brings that actual, already-incurred project performance into the forecast, so the forecast reflects work already performed, cost already incurred, revenue already earned, and current progress, instead of only the original estimate. Connecting a snapshot is the point where the forecast's estimate must be reconciled with what has actually happened. Snapshot Matching determines how that reconciliation affects ETC and EAC.
is a setting on the forecast version, set once for the whole version rather than per line, that determines which of ETC or EAC is recalculated when a snapshot's actual values are brought in. It can be changed on the forecast after creation, while the forecast is open for editing; the new setting applies the next time a snapshot is connected, without retroactively changing values already calculated. The two options are ETC Recalculated and EAC Recalculated.
With ETC Recalculated, EAC is fixed and ETC is recalculated when a snapshot is connected. EAC represents the completion forecast; ETC is tracked only as the remaining amount of work.
For example, a forecast line starts with an ETC of 100 hours and an EAC of 100 hours, with no actual hours reported yet. After connecting a snapshot that reports 40 actual hours, the EAC remains at 100 and the ETC is recalculated to 60 (EAC minus the actual hours). The completion forecast is unchanged; the remaining-work estimate is what moved.
With EAC Recalculated, ETC is fixed and EAC is recalculated when a snapshot is connected. ETC represents an approved estimate of the remaining work; EAC updates automatically to reflect what has actually happened. Using the same starting point, a forecast line with an ETC of 100 hours and an EAC of 100 hours, connecting a snapshot that reports 40 actual hours leaves the ETC at 100 and recalculates the EAC to 140 (ETC plus the actual hours). The remaining-work estimate is unchanged; the completion forecast is what moved.
The appropriate choice depends on how forecasts are managed in the organization, and it also determines which value needs attention at each review, since the other one is derived automatically.
| Snapshot Matching | Suits organizations where... | Revise at each review |
| ETC Recalculated | EAC is the primary forecast target, maintained directly, with variance measured against a fixed completion estimate. | EAC, whenever the expected outcome genuinely changes, for example a scope change or a new risk. |
| EAC Recalculated | ETC is treated as the estimate of remaining work, re-estimated at each review. | ETC, with a fresh estimate of the remaining work. |
EAC Recalculated is common for this reason: it lets you focus on re-estimating what remains, while the system keeps the completion forecast current. Either way, if a value has not changed between two consecutive snapshots, confirm that this is because nothing on the project has changed, not because the forecast has not been reviewed.
Snapshot Matching is easy to confuse with a separate, one-time choice made when a new forecast version is created from an existing one: the ETC option (Do Not Set ETC, Based on Previous ETC, or Based on Previous EAC). The ETC option only decides how the new version's starting ETC and EAC values are derived from the version it was created from; Snapshot Matching decides how that version's ETC and EAC subsequently respond every time a snapshot is connected to it. The two are related rather than independent, which is why they are easy to conflate: the ETC option chosen at creation also sets the new forecast's default Snapshot Matching setting.
| ETC Option | Default Snapshot Matching |
| Based on Previous ETC | ETC Recalculated |
| Based on Previous EAC | EAC Recalculated |
Because both settings move together at creation, comparing forecasts created with different ETC options can look like only one setting has any effect. To isolate Snapshot Matching's effect, change it directly on a single forecast rather than comparing forecasts created with different ETC options.
A negative ETC can occur under ETC Recalculated, because ETC is derived as EAC minus the actual/committed cost or hours already reported. If that actual/committed amount exceeds the EAC, the recalculated ETC is negative. For example, a forecast line with an EAC of 100 hours that receives a snapshot reporting 120 actual hours recalculates to an ETC of -20, with the EAC unchanged at 100.
A negative ETC does not indicate a calculation error. It indicates that the forecast no longer reflects the project's expected outcome: more work has been reported than the EAC allowed for. Typical causes include:
Investigate the cause and create a new forecast version with a re-estimated EAC.