Actual Cost (AC)

Actual cost (AC), sometimes written as the actual cost of work performed, is the real money a project has spent on the work completed up to a given date. It is one of the three core figures in earned-value management, the technique that tracks a project's cost and schedule against its plan. Where planned value says what the work should have cost by now and earned value says what the completed work was budgeted to cost, actual cost says what that completed work truly cost — the invoices paid, the hours billed, the materials bought. It is a backward-looking record of spend, drawn from the accounting system rather than an estimate. Because it captures what happened rather than what was intended, actual cost is the anchor that keeps earned-value analysis honest about money.

Actual cost matters because a project can look fine on a plan and still be quietly overspending, and only the real numbers reveal it. Compare actual cost with earned value and you get cost variance — earned value minus actual cost — which tells you whether the work done cost more or less than budgeted. A negative result means the project paid more than planned for what it produced. Managers use that signal early, while there is still time to renegotiate, re-scope, or slow spend. Without a trustworthy actual cost, the whole earned-value picture collapses, because schedule and cost judgments both lean on knowing what has genuinely been spent. That is why disciplined projects reconcile actual cost to the books rather than to optimistic estimates.

The three earned-value figures are easy to blur, so hold them apart. Planned value is the budgeted cost of the work scheduled to be done by a date — the spending plan. Earned value is the budgeted cost of the work actually completed by that date — progress measured in budget terms. Actual cost is the real cost of that completed work — money genuinely spent. Planned value and earned value are both expressed in budgeted dollars; actual cost is expressed in real ones. A project can have earned value above planned value, meaning it is ahead of schedule, yet an actual cost above earned value, meaning it is over budget, at the same time, because schedule and cost are separate questions. Keeping actual cost distinct from the two budget figures is what lets you separate a spending problem from a pace problem.

The comparisons do the work. Earned value minus planned value is schedule variance, a pace signal in budget terms. Earned value minus actual cost is cost variance, a spend signal. Divide earned value by actual cost and you get the cost performance index, a ratio above one meaning the work cost less than budgeted and below one meaning it cost more. None of these are computable without a clean actual cost, which is why it is treated as the factual bedrock rather than a soft estimate. Confusing actual cost with planned value — treating what was spent as if it were what was scheduled — hides overspending entirely. The discipline is to record actual cost from the accounting system and read it against earned value for cost, never against planned value alone.

Use actual cost as the truthful spend record it is, captured consistently and on the same basis as earned value so the two can be compared cleanly. That means agreeing what costs are counted — labor, materials, subcontractors, and the overheads the project bears — and pulling them from the accounting system at the same cutoff date as the progress measurement. It means measuring earned value and actual cost against the same work packages, so a dollar of earned value and a dollar of actual cost describe the same scope. And it means reviewing cost variance and the cost performance index at each reporting point, so a widening gap between what work should have cost and what it did cost is caught while corrective action is still cheap. Actual cost, kept clean, turns budget control from hindsight into steering.

The failure modes are subtle. Booking costs late makes actual cost lag earned value and flatters cost performance until the bills catch up. Counting committed-but-unspent money as actual cost overstates it. Measuring earned value generously while recording actual cost strictly, or the reverse, corrupts the variance. And treating actual cost as a forecast rather than a record invites wishful accounting. The remedy is boring but decisive: reconcile actual cost to the ledger, align its scope and timing with earned value, and let the comparison — not hope — say whether the project is over or under budget. Done this way, actual cost is the number that keeps an earned-value system connected to reality rather than to the plan everyone wishes were still true.

Actual cost (AC) — the real cost incurred for completed project work — is the earned-value figure compared with planned value and earned value to reveal cost variance.

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