Calculate the Lerner Index from price and marginal cost, then compare pricing power, price-cost margin, markup per unit.
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Market power worksheet
Calculate the Lerner Index, then compare your price-cost margin against common market-power bands.
Use an example scenario or your own price and marginal cost estimate to review the Lerner Index, markup per unit, the implied elasticity benchmark, and what the same marginal cost would look like under tighter or stronger pricing power.
Built for market power, pricing power, and price-cost margin checks This market power calculator keeps the core Lerner index formula but adds benchmark price planning so you can see how the same marginal cost would behave under more competitive, moderate, or stronger pricing conditions.
Example scenarios
A moderate example for a route with some differentiation but real cost pressure.
Display currency
Switch the currency formatting for price and markup outputs without changing the Lerner Index calculation itself.
Result
25%
Moderate pricing power
Lerner Index as a share of price. Decimal form:
0.25.
Markup per unit
$50.00
Marginal cost share
75%
Implied elasticity benchmark
|e| ≈ 4
Pricing-power worksheet
Price
$200.00
Marginal cost
$150.00
Marginal cost share of price
75%
Lerner Index in decimal form
0.25
Markup on marginal cost
33.33%
Implied elasticity benchmark
|e| ≈ 4
Same marginal cost, different benchmark prices
Holding marginal cost constant, these benchmark rows show the price and markup that would correspond to common Lerner Index ranges used in market-power discussions.
Band
Target index
Target price
Markup per unit
Gap vs current price
Competitive pressure
Price stays close to marginal cost and leaves little room for sustained markup.
10%
$166.67
$16.67
-$33.33 (-16.67%)
Managed pricing power
The firm keeps a visible price-cost margin but still operates below strong monopoly-style markups.
25%
$200.00
$50.00
In line with current price
Strong market power
A large share of price sits above marginal cost and would usually require clear barriers, differentiation, or inelastic demand.
50%
$300.00
$150.00
+$100.00 (50%)
Interpretation A meaningful share of price is markup over marginal cost, which points to moderate pricing power if the marginal-cost estimate is reliable.Treat marginal cost as the fragile assumption The Lerner Index is only as good as the marginal-cost estimate behind it. If you are using average variable cost or a blended operating cost as a proxy, test multiple cost assumptions before drawing pricing, strategy, or antitrust conclusions.
Model note
The Lerner Index is a simplified price-cost margin based on marginal cost, not average cost. The implied elasticity benchmark only applies under the standard monopoly first-order condition, and the benchmark-price table holds marginal cost constant purely for scenario planning.
Lerner Index calculator guide: market power, price-cost margin
A Lerner Index calculator turns price and marginal cost into a market power estimate, but a useful page should do more than return a ratio. This calculator also works as a pricing power calculator and price-cost margin worksheet: it shows the Lerner index in decimal and percentage form, the markup per unit, the share of price explained by marginal cost, the textbook elasticity benchmark, and benchmark prices for common competitive-pressure bands.
What the Lerner Index is actually measuring
The Lerner Index measures how far price sits above marginal cost as a share of price. In formula form, it is L = (P - MC) / P. If price equals marginal cost, the index is zero. As price rises further above marginal cost, the index rises toward one.
That is why the measure is often called a market power indicator, a pricing power measure, or a price-cost margin screen. It is not asking whether a business is profitable in an accounting sense. It is asking how much room the firm has to price above the incremental cost of serving one more customer or producing one more unit.
This is also why the input that matters most is marginal cost rather than average cost. A business with large fixed overhead can still have a modest Lerner Index if the selling price sits close to the cost of one more unit. The opposite can also happen in businesses with very low incremental cost, where the price-cost margin looks large even though fixed-cost recovery, product development, and market dynamics still matter.
Formula, supporting outputs, and why the extra views matter
The headline formula is simple, but one ratio rarely gives enough context to make a real decision. That is why this page also shows markup per unit, marginal-cost share of price, markup on marginal cost, and the implied elasticity benchmark from the standard monopoly rule. Those supporting outputs help you see the same market power calculation from several angles.
Markup per unit matters because managers often think in currency before they think in ratios. Marginal-cost share tells you how much of the selling price is still explained by incremental cost. Markup on marginal cost shows the same relationship from the cost base. And the elasticity benchmark provides a textbook bridge to monopoly-pricing theory when the simplifying assumptions are reasonable.
A stronger Lerner index calculator also needs scenario depth. Holding marginal cost constant, this page shows what price would correspond to common benchmark bands such as competitive pressure, managed pricing power, and strong market power. That does not prove the market should price there, but it does make the number easier to interpret than a bare percentage alone.
L = (P - MC) / P
The Lerner Index equals the price-cost margin divided by price.
markup per unit = P - MC
This expresses the same gap in currency terms instead of index form.
MC share of price = MC / P x 100
Shows how much of the selling price is still explained by marginal cost.
|e| ≈ 1 / L
A textbook elasticity benchmark that follows only under the standard monopoly first-order condition.
target price for a benchmark band = MC / (1 - L target)
Used here to compare the same marginal cost under different benchmark Lerner ranges.
How to interpret Lerner Index values without over-claiming
A low Lerner Index generally means price sits close to marginal cost, which is more consistent with strong competition or highly price-sensitive demand. A moderate value suggests the firm has some ability to hold price above incremental cost. A high value suggests stronger pricing power, but not necessarily unlawful or monopolistic conduct by itself.
That final caveat matters. A high price-cost margin can arise from patents, branding, switching costs, network effects, capacity limits, regulation, or product differentiation. In sectors with very large fixed costs, low short-run marginal cost can make the Lerner Index look high even when the broader economics are more complicated. The ratio is therefore best used as a screen, not as a final legal or strategic conclusion.
Competitor pages often stop at broad ranges such as low, moderate, and high market power. That is useful, but still incomplete. The more useful question is whether your marginal-cost estimate is trustworthy, whether the result is stable across a reasonable range of costs, and whether market structure evidence points in the same direction. That is why analysts often pair Lerner-style pricing power checks with concentration tools such as HHI and with direct demand-elasticity work.
A value near 0 means price is close to marginal cost, which is the classic perfect-competition benchmark.
A moderate value does not automatically mean monopoly; it can reflect differentiation, switching costs, or short-run constraints.
A high value should trigger more scrutiny of the marginal-cost estimate before it triggers a hard conclusion about market power.
The same ratio can mean different things across retail, airlines, software, pharmaceuticals, utilities, and other sectors.
Worked examples across different market structures
Suppose price is 200 and marginal cost is 150. The Lerner Index is (200 - 150) / 200 = 0.25, or 25%. That is a useful moderate example because the firm is pricing above marginal cost, but most of the final price still reflects incremental cost. The markup per unit is 50, the marginal-cost share is 75%, and the textbook elasticity benchmark is 4.
Now compare that with a software-style example where price is 500 and marginal cost is 50. The Lerner Index becomes 0.90. That does not automatically prove monopoly, but it does tell you that price sits far above incremental serving cost and that market power, switching costs, fixed-cost recovery, or product differentiation deserve a closer look. It also shows why low-marginal-cost businesses can produce very high Lerner values.
A tighter consumer-goods example might use price 100 and marginal cost 92. The index is only 0.08, so price remains close to cost and the room for sustained markup is thin. This is a better fit for highly competitive categories, commodity-like retail lines, or markets where substitutes are easy to find. Running these side-by-side examples gives more intuition than one abstract formula ever will.
How to estimate marginal cost more carefully
The main practical challenge with any Lerner index calculation is the marginal-cost input. Many teams do not observe true marginal cost directly, so they use average variable cost, contribution cost, or a narrow incremental servicing estimate as a proxy. That can still be useful, but it should be disclosed as an approximation because the final market power estimate moves directly with that assumption.
The safest workflow is to treat marginal cost as a range, not as a single perfect number. If you believe marginal cost is probably between 58 and 65, run each case. If the Lerner Index still lands in the same interpretation band, confidence improves. If the result swings from low pricing power to high pricing power, then the conclusion is fragile and should be reported that way.
This is also the point where a pricing power calculator becomes more useful than a thin formula page. Seeing how benchmark prices change across several plausible marginal-cost assumptions helps analysts, students, founders, and policy teams understand whether the pricing-power story is robust or whether it depends on one uncertain cost estimate.
Lerner Index vs markup, margin, HHI, and elasticity
The Lerner Index is not the same thing as a standard markup calculator or gross margin calculator. Markup and gross margin can be calculated from ordinary cost and price data, but the Lerner Index specifically uses marginal cost. That makes it closer to an economics and antitrust tool than to a basic pricing worksheet, even though the formulas may look superficially similar.
It also differs from HHI. HHI measures market concentration from market shares, while the Lerner Index measures price-cost margin at the firm or product level. A concentrated market can still produce modest Lerner values if pricing remains disciplined, and a differentiated niche business can sometimes show a strong Lerner value even in a broader market that is not highly concentrated.
Elasticity sits somewhere in between. Under the standard monopoly condition, the Lerner Index connects directly to the inverse of the absolute value of demand elasticity. That is a useful teaching relationship and a helpful benchmark, but it should not be mistaken for a full empirical demand estimate unless the market structure assumptions actually fit the case you are studying.
This page is useful for economics coursework, pricing discussions, market-structure screening, and first-pass strategy analysis. It helps answer search-intent questions such as how to calculate the Lerner Index, what a price-cost margin means, how to interpret market power from price and marginal cost, and what price would correspond to a lower or higher benchmark Lerner value.
What it cannot do is prove monopoly power, predict litigation outcomes, or replace sector-specific cost modelling. A high result may still be economically normal in a low-marginal-cost industry, and a low result does not rule out other forms of market power such as bundling, foreclosure, or non-price competition. Use the output as a structured screen and pair it with broader evidence before making material pricing, investment, or legal decisions.
Frequently asked questions
What is the Lerner Index in simple terms?
The Lerner Index measures how much of a product's price sits above marginal cost. A value of 0 means price equals marginal cost, while higher values mean a larger price-cost margin and therefore more room for pricing power.
What is the Lerner Index formula?
The standard formula is L = (P - MC) / P, where P is price and MC is marginal cost. This calculator also shows the same result as markup per unit, marginal-cost share of price, markup on marginal cost, and a textbook elasticity benchmark.
Is the Lerner Index the same as markup or gross margin?
No. Markup and gross margin are common business pricing measures, but the Lerner Index specifically uses marginal cost rather than average or accounting cost. That makes it more of a market power and industrial organization metric than a standard gross-margin output.
What counts as marginal cost in this calculator?
Marginal cost means the cost of producing or serving one more unit. In practice, people often use an estimate or proxy such as average variable cost when true marginal cost is not directly observable. If you do that, treat the Lerner result as an estimate and test a range of plausible costs.
What does a Lerner Index of zero mean?
It means price equals marginal cost in the scenario entered. In textbook microeconomics that is the benchmark associated with perfect competition, where firms have no room to price above incremental cost.
Can the Lerner Index be negative?
A negative value would mean marginal cost is above price. This page treats that as an invalid worksheet input because the standard Lerner interpretation is built for non-negative price-cost margins.
How does the Lerner Index relate to elasticity of demand?
Under the standard monopoly pricing condition, the Lerner Index is approximately the inverse of the absolute value of price elasticity of demand. More elastic demand tends to push the index lower, while more inelastic demand allows higher markups. Outside that simplified model, the elasticity figure should be treated as a benchmark rather than a direct estimate.
Does a high Lerner Index prove monopoly power or antitrust harm?
No. It is a useful screening metric, not a final verdict. Analysts still need to examine market definition, barriers to entry, substitution, regulation, product differentiation, and the reliability of the marginal-cost estimate before drawing legal or strategic conclusions.
