Definition
Pre-calculation is the cost estimate made before a part is manufactured, based on its routing, requirements and factory rates. Post-calculation compares that estimate against what actually happened during production, using production actuals, to check accuracy and improve future estimates.
Why post-calculation only helps when compared against the original estimate
The value of post-calculation depends on consistently comparing it against the original pre-calculation, not just recording what happened; without that comparison, a factory can't tell whether its estimating is systematically too high, too low, or accurate.
Where each activity happens
Neither appears on the drawing; both are estimating and accounting activities that use the drawing and routing as input rather than being specified by them.
Common mistakes
Doing post-calculation without feeding the findings back into future pre-calculation practice; the comparison is only valuable if it actually improves the next estimate.
The value of post-calculation depends on consistently comparing it against the original pre-calculation, not just recording what happened; without that comparison, a factory can't tell whether its estimating is systematically too high, too low, or accurate.
See how Blake reviews a partFrequently asked questions
Which comes first, pre-calculation or post-calculation?
Pre-calculation, before production; post-calculation happens afterward, comparing the estimate to what actually occurred.
Does post-calculation always reveal the pre-calculation was wrong?
Not necessarily; sometimes it confirms the estimate was accurate, which is also valuable information for future confidence in similar estimates.
Why bother with post-calculation if the job is already done?
Because the comparison improves the accuracy of future pre-calculations on similar parts, which compounds in value over many orders.