The Learning Curve: Wright's Law and the 80% Curve With Hours per Unit
October 29, 2026
The learning curve (or experience curve) says that each time cumulative output doubles, the time or cost per unit falls by a fixed percentage. An 80% curve means the time to build unit 2 is 80% of unit 1, unit 4 is 80% of unit 2, unit 8 is 80% of unit 4, and so on. The formula is T(n) = T₁ × n^b, where b = log₂(learning rate) = log₂(0.8) = −0.3219.
If the first unit takes 100 hours, the second takes 80, the fourth 64, the eighth 51.2, and the sixteenth 40.96 hours.
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For unit 10, T = 100 × 10^−0.3219 = 47.7 hours. Cumulative hours for the first 8 units: the sum of 100 × n^b for n = 1 to 8 is about 534.6 hours, an average of 66.8 hours per unit. For 16 units, the total is about 892 hours, an average of 55.8 hours. At a labor cost of $40 an hour, unit 1 costs $4,000 in labor, unit 8 costs $2,048, and the average of the first 16 units is $2,230. The curve flattens: the gains from learning diminish in absolute terms as production continues, but the percentage drop per doubling stays the same.
| Unit number | Hours (80% curve, T1 = 100) | Labor at $40/hour |
|---|---|---|
| 1 | 100.0 | $4,000 |
| 2 | 80.0 | $3,200 |
| 4 | 64.0 | $2,560 |
| 8 | 51.2 | $2,048 |
| 16 | 41.0 | $1,638 |
Where It Applies
Aircraft and shipbuilding (typical learning rates of 75% to 85%), electronics manufacturing, surgical procedures, and software teams on repeated tasks. Wright's Law in the manufacturing literature is the same observation applied to costs: for solar modules and batteries, each doubling of cumulative production has cut prices by roughly 20%. Use it for bidding on production contracts, planning staffing for ramp-up, and estimating when a product reaches a target cost.
Estimating the Rate
Given two data points, for example unit 1 at 100 hours and unit 8 at 55 hours, the rate is (55 ÷ 100)^(1/3) = 0.82, an 82% curve, because 8 is three doublings. Plot unit times against cumulative output on log-log axes, where a constant learning rate gives a straight line. Compare with the actual data and revise the curve.
Cautions
Learning isn't automatic; it depends on repetition, stable design, and management attention. Design changes can reset it, and the curve eventually flattens when processes reach their physical or organizational limits. Use ranges for planning instead of precise values.
Frequently Asked Questions
What does an 80% learning curve mean?
Each doubling of cumulative output reduces the unit time to 80% of its previous value.
What is the formula?
T(n) = T₁ × n^b, with b = log₂ of the learning rate.
How long does unit 8 take on an 80% curve starting at 100 hours?
51.2 hours.
Where is it used?
Manufacturing bids, ramp-up planning, and cost forecasts.
Does learning continue forever?
No, gains flatten as processes mature.