Actual cost (AC) is the realized cost incurred for the work actually performed on an activity during a specific time period.
How It Works in Practice
AC is one of the three core measurements in earned value management, alongside planned value (PV) and earned value (EV). It comes from real financial records, timesheets, invoices, and purchase orders, not from estimates. Comparing AC to EV gives the cost variance (CV) and cost performance index (CPI), the numbers project managers use to tell whether a project is running over or under budget.
Where It Fits in PMBOK 8
PMBOK 8 keeps AC as one of the standard earned value terms used in the Measurement performance domain, alongside PV, EV, EAC, ETC, and BAC, to track cost performance objectively rather than by gut feeling.
FAQ
Is actual cost the same as budget? No, budget (planned value) is what you expected to spend; actual cost is what you really spent.
How is actual cost used to forecast the final cost? It feeds into the estimate at completion (EAC), typically as AC plus a re-forecast of the remaining work.
By Tom, PMP-certified since 2004. Last updated: July 2026