Lost profits
Lost profits are the supra-royalty measure of patent damages awarded when the patentee proves it would have made the infringer's sales but for the infringement. The Federal Circuit applies the four-factor Panduit test as the canonical, though not exclusive, route to recovery, supplemented by market-share apportionment, convoyed-sales doctrine, price erosion, and — for foreign sales tied to domestic infringement under § 271(f) — the rule of WesternGeco.
The rule
A patentee may recover lost profits where the record establishes a "reasonable probability that, but for the infringement, [the patentee] would have made the sales that were made by the infringer." Rite-Hite Corp. v. Kelley Co., 56 F.3d 1538, 1545 (Fed. Cir. 1995) (en banc) (quoting King Instruments Corp. v. Perego, 65 F.3d 941, 952 (Fed. Cir. 1995)). Lost profits compensate for foregone sales and the consequences that flow from them — price erosion, lost convoyed sales, and increased per-unit costs. They exceed the statutory reasonable-royalty floor and are awarded only where the patentee carries the higher burden of "but for" causation.
Statutory and constitutional source
Section 284 commands damages "adequate to compensate for the infringement." 35 U.S.C. § 284. Although the statute names only "reasonable royalty" as the floor, the Supreme Court and the Federal Circuit have long read "adequate to compensate" to authorize recovery of the patentee's actual lost profits where they can be proven. Aro Mfg. Co. v. Convertible Top Replacement Co., 377 U.S. 476, 507 (1964) (the patentee is entitled to "the difference between his pecuniary condition after the infringement, and what his condition would have been if the infringement had not occurred"). See Title 35 reference.
The constitutional source is the same as for all patent remedies: the exclusive right secured by Article I, § 8, cl. 8, vindicated through compensatory damages.
The framework the courts apply
The Panduit four-factor test
The Sixth Circuit's opinion in Panduit Corp. v. Stahlin Bros. Fibre Works, Inc., 575 F.2d 1152, 1156 (6th Cir. 1978), authored by then-Judge Markey sitting by designation, articulated four elements that, if proved, give rise to an inference of "but for" causation:
- Demand for the patented product.
- Absence of acceptable non-infringing substitutes.
- Manufacturing and marketing capacity to exploit the demand.
- The amount of profit that the patentee would have made.
The Federal Circuit adopted Panduit as one but not the only path to lost profits. Rite-Hite, 56 F.3d at 1545. A patentee may also prove lost profits through reliable economic analysis even where one Panduit factor is in doubt.
Demand and acceptable substitutes
"Demand for the patented product" is generally satisfied by the infringer's own sales: an infringer's market acceptance is itself evidence that demand exists. Gyromat Corp. v. Champion Spark Plug Co., 735 F.2d 549 (Fed. Cir. 1984). The "acceptable non-infringing substitute" inquiry is more demanding. A substitute is acceptable only where it has the "advantages of the patented product" that drove customer demand. Standard Havens Prods., Inc. v. Gencor Indus., Inc., 953 F.2d 1360 (Fed. Cir. 1991). Available but inferior alternatives are not enough; a substitute must be both available during the damages period and acceptable to customers.
The Federal Circuit has held that the patentee need not be the only supplier. In a multi-supplier market, the patentee may recover lost profits on its proportional share of the infringer's sales using the market-share approach of State Indus., Inc. v. Mor-Flo Indus., Inc., 883 F.2d 1573 (Fed. Cir. 1989). The patentee proves its market share among non-infringing suppliers and recovers lost profits on that share, with the balance compensated as a reasonable royalty.
Manufacturing and marketing capacity
The patentee must show it could have made and sold the additional units. Capacity is generally proved through evidence of plant utilization, distribution, sales force, and the ability to ramp up. Tight capacity constraints may cap recovery; idle capacity supports a full lost-profits award.
Quantum of profit
The amount recoverable is the incremental profit on the lost sales — generally revenue minus incremental (variable) costs, not full absorption costs. Paper Converting Mach. Co. v. Magna-Graphics Corp., 745 F.2d 11, 22 (Fed. Cir. 1984). Fixed costs do not reduce the recovery if they would have been incurred regardless of the additional sales.
Convoyed sales and Rite-Hite foreseeability
Convoyed sales are unpatented items so closely associated with the patented product that the patentee would have sold them along with the patented item. Rite-Hite, 56 F.3d at 1549–51, held that convoyed sales are recoverable only where the unpatented and patented components together "constitute a functional unit" or "are analogous to components of a single assembly." Items merely sold together for marketing convenience do not qualify. Am. Seating Co. v. USSC Grp., Inc., 514 F.3d 1262 (Fed. Cir. 2008).
The en banc Rite-Hite majority also extended lost-profits recovery to a non-infringing product line that competed with the infringer where those losses were "reasonably foreseeable." 56 F.3d at 1546. The court awarded lost profits on the patentee's manual product line, even though that line did not practice the patent, because the infringer's sales of an infringing motorized product diverted those manual sales.
Price erosion
Where the infringer's competition forced the patentee to lower its prices below those it would have charged in an infringer-free market, price erosion is recoverable. Crystal Semiconductor Corp. v. Tritech Microelectronics Int'l, Inc., 246 F.3d 1336 (Fed. Cir. 2001), set out the framework: the patentee must prove that, but for the infringement, it would have charged a higher price; account for the elasticity of demand at that higher price; and show the volume of sales it would have made at that higher price. Theoretical price-erosion theories without market evidence are routinely excluded under Daubert.
Extraterritorial lost profits — § 271(f) and WesternGeco
WesternGeco LLC v. ION Geophysical Corp., 585 U.S. 407 (2018), held that a patentee may recover lost profits flowing from foreign sales where infringement under 35 U.S.C. § 271(f)(2) — the supply of components from the United States for combination abroad — is the cause. The Court applied the two-step extraterritoriality framework of RJR Nabisco, Inc. v. European Cmty., 579 U.S. 325 (2016): § 284's damages remedy is focused on infringement; the conduct relevant to that focus (the supply of components from the United States) was domestic; and the foreign sales were the foreseeable consequence of that domestic conduct. The Court did not address whether the same logic extends to direct infringement under § 271(a) for foreign losses.
Burden and proof
The patentee bears the burden by a preponderance of the evidence. SmithKline Diagnostics, Inc. v. Helena Labs. Corp., 926 F.2d 1161, 1164 (Fed. Cir. 1991). The Panduit factors create a rebuttable inference of "but for" causation; satisfying them does not entitle the patentee to lost profits if the infringer rebuts with evidence that some sales would have been lost to acceptable substitutes.
Causation evidence may include economic models, customer testimony, win/loss data, and head-to-head competition records. Pure speculation does not suffice. Lam, Inc. v. Johns-Manville Corp., 718 F.2d 1056 (Fed. Cir. 1983).
Interaction with related doctrines
Lost profits and a reasonable royalty are alternative measures and may be combined. A patentee that proves lost profits on, say, 60 percent of the infringer's units, may recover a reasonable royalty on the remainder. See reasonable royalty. The combined recovery is then subject to enhancement under § 284. See willfulness and enhanced damages.
The marking and notice requirements of 35 U.S.C. § 287(a) cap recovery in product cases. The six-year limitation on damages in 35 U.S.C. § 286 limits the look-back regardless of when the suit is filed.
Lost-profits theories interact closely with literal infringement and the doctrine of equivalents — the scope of infringement defines the universe of unit sales subject to damages. Claim construction typically precedes any damages analysis. After WesternGeco, lost-profits theories also extend, in qualifying cases, to foreign sales caused by domestic conduct under § 271(f).
Practical notes
Expert reports and Daubert
Lost-profits expert reports must:
- Identify the relevant market and define market share with reference to record evidence.
- Address each Panduit factor with admissible underlying data.
- Quantify acceptable non-infringing substitutes and explain why they did or did not divert sales.
- Use incremental cost — not full absorption cost — to compute lost profit per unit.
- Where a Mor-Flo theory is used, support the patentee's market share with reliable industry data.
- Where price erosion is alleged, reconcile the proposed higher price with demand elasticity.
Common Daubert vulnerabilities include reliance on aggregate market data without unit-level analysis, treating any competing product as an infringing diversion, and ignoring the existence of actual substitutes.
Discovery
Lost-profits cases drive substantial third-party discovery. The infringer typically subpoenas the patentee's customers; the patentee subpoenas the infringer's customers and resellers. Sales-by-customer data and bid records are central. Protective-order treatment is universally required.
Jury instructions
Most district courts instruct on Panduit by the four-factor name. Where the patentee proceeds on a Mor-Flo theory, the instruction explains that lost profits are recoverable on the patentee's market share, and a reasonable royalty on the remainder.
Standing and assignment issues
Only the patent owner with all substantial rights has standing to recover lost profits. An exclusive licensee may join a co-owner; bare licensees cannot recover lost profits on their own.
Open questions
- Extraterritorial reach beyond § 271(f). The Federal Circuit has begun to extend WesternGeco reasoning to other infringement theories, but the boundary — for example, induced infringement under § 271(b) leading to foreign acts — is unsettled. Power Integrations, Inc. v. Fairchild Semiconductor Int'l, Inc., 904 F.3d 965 (Fed. Cir. 2018), declined to apply foreign lost profits in a § 271(a) case before WesternGeco.
- Convoyed sales of services and software updates. Application of the Rite-Hite "functional unit" test to subscription, software, and service revenue is still being developed in the district courts.
- Two-supplier presumption. Whether and when a court should apply a presumption of full diversion in a duopoly market continues to draw varying treatment.
See also
- Reasonable royaltyThe statutory floor and the alternative damages measure to lost profits.
- Willfulness and enhanced damagesWhen a court may enhance damages up to threefold under Halo.
- Permanent injunctionsForward-looking equitable relief governed by the eBay four-factor test.
- Indirect infringementSection 271(f) supply abroad and § 271(b)/(c) inducement and contribution.
- Exceptional case attorneys' feesFee-shifting under § 285 after Octane Fitness.
- eBay v. MercExchangeThe four-factor test for permanent injunctions in patent cases.
Last reviewed: 2026