How to review estimated versus actual job costs

A completed job is useful evidence for the next quote. Compare its estimate with actual work using the same scope and cost definitions. Otherwise a variance can reflect mismatched records rather than poor performance.

Reconcile the whole job first

A hypothetical job was sold for 2,000. Estimated costs were 600 of labour, 500 of materials and 100 of other costs. Actual costs were 756, 560 and 120. Neither column includes general overhead in this example.

Item	Estimate	Actual	Actual minus estimate
Labour	600	756	+156
Materials	500	560	+60
Other	100	120	+20
Included costs	1,200	1,436	+236
Contribution after included costs	800	564	−236

The margin on included costs falls from 40% to 28.2%. This is not net profit because overhead and other omitted expenses remain. Enter the two columns in the job costing worksheet and keep the signed quote, supplier bills and time records with the job.

Split labour hours from labour rate

The estimate assumed 20 hours at 30. Actual work took 24 hours at 31.50. One exact decomposition uses:

• Hours effect: (24 − 20) × 30 = 120.
• Rate effect: (31.50 − 30) × 24 = 36.
• Total: 120 + 36 = 156.

The rate effect uses actual hours so the two effects reconcile fully. If both effects used only estimated quantities, the interaction between rate and hours would be left out. There are other valid decompositions; state the convention and use it consistently.

Find the operational cause

Extra hours may come from an omitted task, access delays, rework, travel or approved additional scope. Record the reason before concluding that a worker was slow. Higher material cost may be a higher unit price, greater quantity, lower usable yield or a change in specification. Separate these where records allow it.

If the customer approved extra work, compare that work and its additional revenue separately, then reconcile the complete job. Do not add the cost of a change to the original scope while leaving the change revenue out of the review.

Turn the result into a better estimate

Use repeated observations to update standard task hours, purchasing assumptions or scope wording. One unusual job is not a reliable average. Keep original estimates intact, record why the next assumption changed and watch whether the change improves later estimates.

Update labour cost per billable hour only when the underlying period costs or available hours have changed. A single job overrun belongs first in the job estimate. If extra scope is the recurring cause, improve change pricing and approval records.

Method and scope

All amounts above are hypothetical teaching figures in one currency, excluding tax unless stated otherwise. These are original scenarios, not market prices, benchmark targets or professional recommendations. The references support the underlying concepts, not the example assumptions. This AI-assisted explanation has not had independent professional review. Calculation methods and limitations.