A flexible budget restates the original budget at the activity level you actually reached: variable costs are recomputed at actual volume, fixed costs stay where they were. That makes performance comparisons fair — actual results get judged against what costs should have been at the volume that actually happened, not at a volume someone guessed months earlier. Without it, a busy month looks wasteful and a slow month looks efficient, purely because volume moved.
The flexible budget also splits the total budget miss into two pieces that have different causes and different owners. The flexible-budget variance (actual vs flexed) measures spending and efficiency at the real volume. The volume variance (flexed vs static) measures nothing but the activity difference. Exam questions on budgeting and variance analysis almost always come down to keeping those two apart.
A static budget is built once, before the period starts, at one planned volume. It never moves, no matter what actually happens. That is fine for planning — you need one set of numbers to commit to — but it breaks down as a performance benchmark the moment actual volume differs from plan.
Here is the problem. Suppose a department budgeted costs for 8,000 units and then produced 9,200. Actual costs will almost certainly exceed the static budget, because 9,200 units genuinely cost more to make than 8,000. If you compare actuals straight against the static budget, the report screams over budget — but you cannot tell whether the manager overspent or the department simply did more work. One comparison is mixing two questions: did we control spending, and did volume differ from plan?
The flexible budget separates them. It asks: at 9,200 units, what should each cost line have been? Variable costs move with activity, fixed costs do not — the same cost behavior that drives contribution margin analysis. So the flexed budget recomputes each variable line at the actual volume and carries each fixed line unchanged.
Three steps, applied line by line:
flexed amount = budgeted rate × actual volume.The flexed total is what the period should have cost at the volume that actually occurred. One caveat: budgeted rates and fixed amounts only hold inside the relevant range. If actual volume lands far outside what the rates were built for — a second shift, new equipment — the flexed numbers need rebuilding, not just rescaling.
Here is a full department run, planned at 8,000 units with 9,200 actually produced.
| Cost line | Static budget (8,000 units) | Flexed budget (9,200 units) | Actual (9,200 units) | Flexible-budget variance | Volume variance |
|---|---|---|---|---|---|
| Direct materials — $3.25 per unit | $26,000 | $29,900 | $30,820 | $920 U | $3,900 U |
| Direct labor — $2.10 per unit | $16,800 | $19,320 | $18,975 | $345 F | $2,520 U |
| Variable overhead — $0.85 per unit | $6,800 | $7,820 | $8,140 | $320 U | $1,020 U |
| Fixed overhead (rent, supervision) | $11,400 | $11,400 | $11,650 | $250 U | $0 |
| Total | $61,000 | $68,440 | $69,585 | $1,145 U | $7,440 U |
Walk one line to see the mechanics. Direct materials were budgeted at $3.25 per unit, so the flexed amount is $3.25 × 9,200 = $29,900. Actual materials cost $30,820, so the flexible-budget variance is $30,820 − $29,900 = $920 unfavorable — the department spent $920 more on materials than 9,200 units justified. The volume variance is $29,900 − $26,000 = $3,900 unfavorable — the cost of making 1,200 extra units, at budgeted rates.
Fixed overhead is the mirror image. It does not flex: the flexed column repeats the $11,400 static amount, so its volume variance is $0 by construction. The $250 unfavorable flexible-budget variance is real spending above plan — perhaps a rent increase or overtime for the supervisor.
And the columns tie. Total actual $69,585 minus total static $61,000 is a total static-budget variance of $8,585 unfavorable, which splits exactly into $1,145 U of spending (flexible-budget variance) and $7,440 U of volume. Every flexible budget problem should tie this way; if yours does not, a variable line was not flexed or a fixed line was.
Direction first. For costs, actual above the flexed budget is unfavorable and below is favorable — spending less than the volume justified helps income. For revenue, the signs flip: actual above the flexed budget is favorable. Favorable never means smaller; it means better for operating income.
The two variances point at different causes. The flexible-budget variance is the controllable piece: prices paid, hours used, waste, efficiency — things the department manager influences at the volume that actually happened. The $345 favorable labor line above says the crew ran cheaper than $2.10 per unit; the $920 unfavorable materials line says usage or price ran high. These are the numbers worth investigating.
The volume variance is purely arithmetic about activity. Here it is $7,440 unfavorable on costs because the department made 1,200 more units than planned — but making more units is usually good news once the extra revenue is counted. A flexible budget performance report presents exactly this split: actual results, the flexed budget, and the static budget side by side, so spending questions and volume questions each get their own column.
Flexing fixed costs. The most common error is multiplying every line by the volume ratio (9,200 ÷ 8,000) — which restates fixed overhead at $13,110 and breaks the whole table. Fixed costs do not move with volume inside the relevant range. If a line is fixed, the flexed column repeats the static number, full stop.
Reading F and U as small and large. Students see a favorable variance and assume actual was below budget. True for costs, backwards for revenue. Anchor on operating income: favorable pushes income up, unfavorable pushes it down, whichever side of the budget the actual lands on.
Blaming managers for the volume variance. An unfavorable cost volume variance is not overspending — it is the budgeted cost of extra output. A production supervisor does not control customer demand, so grading them on the static-budget comparison punishes them for a busy month. Evaluate spending against the flexed budget; trace volume back to sales forecasts and demand.
Flex the budget to actual volume before judging anything: the flexible-budget variance (actual vs flexed) isolates spending control, the volume variance (flexed vs static) isolates activity, and the two always sum to the total static-budget variance.
A flexible budget is the original budget restated at the actual activity level. Each variable cost line is recomputed as budgeted rate per unit times actual volume, and each fixed cost line stays at its original budgeted amount. It answers the question: what should this period have cost at the volume we actually hit?
Classify each line as variable or fixed. For variable lines, find the budgeted rate per unit (static amount divided by planned units) and multiply it by actual units — $3.25 per unit at 9,200 actual units flexes to $29,900. For fixed lines, carry the static amount unchanged. The rates only hold inside the relevant range.
It shows three columns side by side: actual results, the flexed budget at actual volume, and the static budget at planned volume. Actual minus flexed gives the flexible-budget variance (spending and efficiency); flexed minus static gives the volume variance (activity). Together they explain the entire gap between actual results and the static budget.
A static budget is fixed at one planned volume before the period starts and never changes. A flexible budget adjusts variable costs to the volume that actually occurred while holding fixed costs. Static budgets work for planning and commitments; flexible budgets are the fair benchmark for evaluating performance after the fact.
Because fixed costs — rent, salaries, depreciation — do not vary with volume inside the relevant range, producing 9,200 units instead of 8,000 does not change what they should be. If actual fixed spending still differs from budget, that difference shows up as a flexible-budget variance, not a volume effect.