Estimate how long and how much it costs to build a batch of a new product, knowing each unit comes out faster than the last, and find when the crew reaches standard time.
Pre-sizing and estimating tool: results do not replace design, calculations or reports signed by a licensed professional, nor verification against the applicable codes and standards.
Each unit’s time under both models, with the same rate and first-unit time. The shaded band is the batch entered.
Unit time, cumulative average and cumulative total at each doubling of quantity, under both models (no plateau).
Measured points and the fitted line. On log scales the learning curve becomes a straight line.
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It is the rule, seen in production, that the time to make one unit falls by a fixed ratio every time cumulative quantity doubles. At an 85% rate, if unit 1 takes 10 h, unit 2 takes 8.5 h, unit 4 7.2 h and unit 8 6.1 h. It is used to quote batches of new products and plan launch labor.
In Wright’s model the rate applies to the cumulative average; in Crawford’s, to each unit’s time. At the same rate Wright gives lower times: in the example, the 100-unit batch takes about 455 h under Crawford and 420 h under Wright. Use the model the rate was measured with.
Best is to fit your own plant’s actual times by pasting them into the fitting box. Without data, use literature ranges: complex manual assembly and electrical operations, 75 to 85%; repetitive welding, about 90%; repetitive machining and stamping, 90 to 95%. The more machine-paced the work, the closer to 100%.
With a 10 h first unit, an 85% rate (Crawford) and a 4 h standard time, standard is reached at unit 50. Units 1 to 100 add up to about 455 h, an average of 4.55 h, and labor cost at US$ 45 an hour is close to US$ 20.5k. The hours above standard, about 55 h, are the cost of learning.
In practice time does not fall forever: once the method settles, it levels off near standard time. With the plateau option, the calculator keeps the curve from dropping below that value. Turn it off to see the full theoretical curve.
From the prototype or pilot batch, timed with the crew that will produce it. Without that, use the first batch of a similar product or multiply the estimated standard time by a start-up factor, usually 1.5 to 3 times in assembly.
It assumes the same crew and method throughout production. Staff turnover, design changes or long stoppages push time back up and partly restart the curve. It also does not apply to the machine-paced part of the cycle, which barely learns.
Important notice: Indus Metrics tools produce estimates and pre-sizing results from the data you enter and from published engineering methods. They do not replace design, calculations or reports signed by a licensed professional engineer (PE), nor verification against the applicable codes, standards and regulations, such as OSHA rules and the ASME codes. Material and fuel properties vary: check manufacturer data or your own process analyses before deciding. By using this site you agree to the Terms of Use.
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