Likelihood of confusion is the engine of almost every U.S. trademark infringement case. It is not a tally where the side with more factors wins; it is a holistic, fact-intensive prediction about whether an appreciable number of ordinary, reasonably prudent consumers are likely to be confused as to the source, sponsorship, or affiliation of goods or services. This checklist gives you a repeatable workflow for performing that analysis—for a clearance opinion, an enforcement decision, a complaint, or a defense. It assumes the doctrinal background covered in Navigating the Maze of Trademark Confusion and, for the summary-judgment posture, Polaroid Factors on Summary Judgment in the Second Circuit.

Work the phases in order. Each - [ ] is an action you can actually perform.

Phase 1 — Frame the question and pick the controlling test

  • Identify the forum and circuit that will (or would) decide the dispute, because the exact factor list and its weighting differ by circuit.
  • Confirm whether you are analyzing registrability (TTAB / Federal Circuit — apply the DuPont factors) or the right to use / infringement (district court — apply the regional circuit's test).
  • Select the controlling list: Polaroid (2d Cir.), DuPont (Fed. Cir./TTAB), Sleekcraft (9th Cir.), or the equivalent regional list (Third Circuit Lapp, Fifth Circuit "digits of confusion," Sixth Circuit Frisch's, etc.).
  • Pin down the legal standard: probability of confusion, not mere possibility, judged by the ordinarily prudent purchaser.
  • Identify which theory or theories of confusion are in play: forward (direct), reverse, sponsorship/affiliation, initial-interest, or post-sale.
  • Note whether confusion is alleged among purchasers or non-purchasers (dealers, brokers, the observing public), since both can be actionable.

WHY / traps. The single most consequential early error is analyzing the wrong test or in the wrong posture. A DuPont registrability analysis compares the marks and goods as recited in the application and registration and presumes all normal trade channels and purchasers; a district-court infringement analysis examines real-world marketplace use. The two can come out differently on identical marks. Flag the theory early, too: in reverse confusion, the strength inquiry shifts to the junior user's commercial saturation, and bad-faith intent to pass off is not required—an easy thing to miss until it sinks the analysis.

Phase 2 — Build the factual record

  • Collect the senior mark exactly as used and as registered (drawing, specimens, registration certificate, first-use dates, status).
  • Collect the junior mark as actually used in the marketplace (packaging, trade dress, house marks, advertising, point-of-sale presentation, web/app screenshots).
  • Document the goods or services of each party, their price points, and conditions of sale.
  • Map the trade channels and marketing channels: where and how each party advertises and sells, and whether those channels actually overlap.
  • Identify the relevant consumers and their sophistication, purchase frequency, and degree of care.
  • Gather any actual-confusion evidence: misdirected emails, calls, orders, invoices, complaints, and dated instances.
  • Investigate third-party use of similar marks on related goods (actual use, not just registrations) to test the senior mark's strength.
  • Pull the adoption history of the junior mark: clearance searches, counsel opinions, internal naming documents.
  • Capture and date web evidence properly (see Capturing the Web).

WHY / traps. Factors talk to each other, and you cannot weigh them without the underlying facts. Two recurring traps: (1) treating a pile of third-party registrations as proof of marketplace weakness—district courts generally require actual, promoted use, though the TTAB and Federal Circuit will credit registrations as evidence of conceptual weakness; and (2) relying on anecdotal "a customer told me they're the same company" hearsay without a non-hearsay purpose. Surveys exist precisely to capture confusion admissibly.

Phase 3 — Analyze each factor

  • Strength of the senior mark — place it on the Abercrombie spectrum (generic / descriptive / suggestive / arbitrary / fanciful) for conceptual strength, then assess commercial strength (duration, advertising spend, sales, media, recognition). Note any incontestable status and any third-party-use dilution of strength.
  • Similarity of the marks — compare sight, sound, and meaning as a whole (anti-dissection rule), in marketplace context, on the basis of imperfect recollection (no side-by-side). Account for house marks and dominant elements.
  • Relatedness / proximity of the goods or services — ask whether consumers would expect the goods to come from the same source; direct competition is not required.
  • Bridging the gap — assess the senior user's likely expansion into the junior user's market, but only where it is publicly known or expected (subjective unannounced intent is irrelevant).
  • Actual confusion — weigh quantity and quality; treat isolated instances as de minimis and note that an extended, overlapping, confusion-free coexistence cuts against confusion.
  • Intent / good faith — distinguish deliberate copying or intent to trade on goodwill (which supports confusion) from mere knowledge of the senior mark (which alone is not bad faith).
  • Marketing/trade channels — assess specific overlap; discount a shared but ubiquitous channel (e.g., "both sell online").
  • Consumer sophistication / degree of care — calibrate to price, importance, frequency, and buyer expertise; remember even careful buyers can be confused by very similar marks on very similar goods.
  • Quality of the junior user's goods — note it cuts both ways and is usually minor.
  • Add any circuit-specific factors (e.g., DuPont's third-party-marks, market-interface, and length-of-concurrent-use factors).

WHY / traps. Resist the urge to score every factor equally. Most circuits treat mark similarity, mark strength, and goods proximity as the heavy hitters; a powerful showing there can outweigh a thin record elsewhere, and dissimilarity alone can defeat confusion. Common mistakes: dissecting marks into shared syllables instead of comparing overall commercial impression; staging an improper side-by-side comparison; and treating "knowledge of the senior mark" as bad faith.

Phase 4 — Decide whether to commission a survey

  • Decide if the case turns on consumer perception enough to justify a survey's cost and lead time.
  • Choose the format: Eveready (senior mark strong/famous; show only the junior mark) or Squirt (weaker mark or marks genuinely seen together; show both, with rigorous controls).
  • Define the universe correctly (prospective purchasers of the junior user's goods for forward confusion; senior user's purchasers for reverse confusion).
  • Require a control cell and report net confusion (test minus control), not the raw figure.
  • Plan for double-blind administration, neutral questions, marketplace-realistic stimuli, and objective coding.

WHY / traps. A mediocre survey is often worse than none—it hands the opponent a Daubert target and a number to attack. Net confusion of roughly 15%+ generally supports confusion; below ~10% tends to negate it; 10–15% is a gray zone. For design and admissibility, see Consumer Survey Expert Methodology in Trademark Cases and Daubert Challenges to Consumer Survey Experts. A dedicated survey workflow lives in the consumer survey design checklist.

Phase 5 — Weigh holistically and document the conclusion

  • Weigh the factors as an integrated judgment, identifying which ones actually move the needle in this market—not by counting.
  • State whether the result is clear or close, and (if litigation is contemplated) whether the key objective factors line up for a possible summary-judgment disposition.
  • Apply any circuit rule that resolves doubt in favor of the senior user.
  • Where the analysis supports adoption of a junior mark, preserve the good-faith record (clearance search + counsel opinion) to defeat willfulness — see The Shield of Good Faith.
  • Write a dated, evidence-cited memorandum that walks each factor, states the weight assigned, and explains the bottom line.
  • Flag any dilution angle separately (famous marks under 15 U.S.C. § 1125(c)) — dilution does not require confusion and has its own elements.

WHY / traps. The conclusion is a prediction, not arithmetic. Document the reasoning so it survives scrutiny by a skeptical adversary, examiner, or judge. Do not let an expressive-use or parody argument lull you—after Jack Daniel's Properties, Inc. v. VIP Products LLC, 599 U.S. 140 (2023), when a defendant uses the borrowed mark as a source identifier for its own goods, the ordinary multifactor analysis applies in full.

Common mistakes

  • Tallying factors instead of weighing them holistically.
  • Using the wrong test for the posture (a DuPont registrability analysis where an infringement analysis is needed, or vice versa).
  • Missing a reverse-confusion theory, then applying strength and intent backward.
  • Comparing marks side-by-side or dissecting them into shared fragments.
  • Equating mere knowledge of the senior mark with bad faith.
  • Relying on third-party registrations (without use) to prove a crowded field in district court.
  • Commissioning a survey on the wrong universe, with no control, or in the wrong format.

Primary authority

  • Statutes: Lanham Act §§ 32, 43(a), 15 U.S.C. §§ 1114, 1125(a); dilution, 15 U.S.C. § 1125(c); definitions, 15 U.S.C. § 1127.
  • Tests: Polaroid Corp. v. Polarad Elecs. Corp., 287 F.2d 492 (2d Cir. 1961); In re E.I. du Pont de Nemours & Co., 476 F.2d 1357 (C.C.P.A. 1973); AMF Inc. v. Sleekcraft Boats, 599 F.2d 341 (9th Cir. 1979).
  • Key cases: Jack Daniel's Props., Inc. v. VIP Prods. LLC, 599 U.S. 140 (2023); Star Indus., Inc. v. Bacardi & Co., 412 F.3d 373 (2d Cir. 2005); Union Carbide Corp. v. Ever-Ready Inc., 531 F.2d 366 (7th Cir. 1976) (Eveready survey); SquirtCo v. Seven-Up Co., 628 F.2d 1086 (8th Cir. 1980) (Squirt survey).
  • Reference: Federal Judicial Center, Reference Manual on Scientific Evidence (Reference Guide on Survey Research); McCarthy on Trademarks and Unfair Competition. USPTO confusion practice resources at uspto.gov.

Verify the controlling circuit's exact factor list and current case law before relying on this analysis.

Related resources

This checklist is general information, not legal advice. Likelihood of confusion is intensely fact-specific; consult qualified trademark counsel about any particular matter.