Patent damages are calculated by determining the monetary compensation attributable to the infringement, based on the economic harm caused by the unauthorized use of the patented invention. The two principal approaches are lost profits suffered by the patent owner and a reasonable royalty for the use of the patented technology. The appropriate measure depends on the evidence available and the circumstances of the case.The calculation generally requires identifying the infringing sales or uses, determining the economic impact of the infringement, and establishing a causal connection between the patented technology and the claimed loss. Damages may also require apportionment where the accused product contains both patented and unpatented features. The analysis is typically performed for each relevant damages period and may account for changes in sales, pricing, royalty rates, and other economic factors over time.

The principal methods are lost profits and reasonable royalty damages. Lost profits attempt to compensate the patent owner for profits it would have earned but for the infringement, while a reasonable royalty represents the amount the parties would reasonably have agreed upon for use of the patented technology.In appropriate circumstances, additional economic considerations may affect the calculation, such as price erosion, convoyed sales, or other losses supported by the evidence. Where lost profits cannot be established reliably, a reasonable royalty often serves as the damages measure. The selected methodology should reflect the available evidence and should not attribute value to the patented technology that is actually generated by unrelated features.

A reasonable royalty is the minimum monetary compensation that a patent owner is entitled to for an infringer's unauthorized use of the patented invention when lost profits are not established or are not the appropriate measure. Conceptually, it represents the royalty that would have resulted from a hypothetical negotiation between a willing patent owner and a willing licensee at the relevant time.The analysis considers the circumstances that would have been known to the parties when the hypothetical negotiation is assumed to occur. Factors can include the strength and importance of the patent, available alternatives, existing licenses, the commercial relationship between the parties, expected profitability, and the portion of the product's value attributable to the patented technology.

A reasonable royalty is generally calculated by estimating an appropriate royalty base and applying a supportable royalty rate:Reasonable royalty = Royalty base × Royalty rateThe royalty base represents the sales or other economic measure to which the rate is applied, while the rate reflects the value of the patented technology and the terms that would have resulted from the hypothetical negotiation. Both components must be supported by evidence; selecting a percentage without establishing an appropriate base or economic rationale can substantially distort the damages calculation.The analysis may use comparable licenses, the parties' negotiating positions, available non-infringing alternatives, profitability, the importance of the patented feature, and the other Georgia-Pacific factors. Where the accused product contains substantial non-patented technology, apportionment may be necessary before applying the royalty rate.

The Georgia-Pacific framework is a set of fifteen factors commonly used to analyze the reasonable royalty that might have resulted from a hypothetical negotiation between the patent owner and infringer. The factors originate from Georgia-Pacific Corp. v. U.S. Plywood Corp. and consider circumstances such as existing licenses, the nature and scope of the patent license, the relationship between the parties, the profitability of the patented product, the commercial success of the invention, the remaining patent term, and the parties' respective bargaining positions.The factors are not a mechanical formula and do not require assigning equal weight to every consideration. Their purpose is to provide a structured framework for assessing the economic circumstances surrounding the hypothetical negotiation. The factors that actually have evidentiary support and relevance should drive the analysis rather than mechanically applying all fifteen.

A royalty rate should be derived from evidence of the economic value of the patented technology, rather than selected solely by reference to industry averages. The analyst typically examines comparable licenses, the profitability and importance of the patented feature, available technical alternatives, the parties' negotiating positions, the duration and scope of the hypothetical license, and other relevant circumstances.Comparable licenses are often particularly informative when they involve the same patent or closely related technology and have sufficiently similar economic circumstances. The proposed rate should also be consistent with the royalty base and with any required apportionment of value between patented and unpatented features. A rate that is economically reasonable in isolation may become unreasonable if applied to an improperly broad royalty base.

Comparable licenses can provide important evidence of the economic value previously placed on the patented technology. Licenses involving the asserted patent, related patents, comparable technologies, or similar commercial circumstances can help establish a reasonable royalty and provide a real-world benchmark for the hypothetical negotiation.However, licenses cannot be treated as directly interchangeable without examining their circumstances. Differences in technology, exclusivity, territory, field of use, royalty structure, cross-licensing arrangements, litigation settlement context, timing, and bargaining power can materially affect the rate. A strong damages analysis therefore explains why a particular license is comparable and what adjustments are necessary, rather than simply averaging royalty rates from unrelated agreements.

Apportionment separates the economic value attributable to the patented invention from value generated by unpatented features, components, and functionality. This is particularly important when the accused product contains many technologies and the patented feature represents only one part of its overall commercial value.The analyst may use technical evidence, consumer demand, feature-level pricing, comparable products, licenses, cost or profitability information, conjoint or survey evidence, and other economic methods to determine the appropriate contribution of the patented technology. The methodology must be tied to the actual patent claim and the value of the claimed invention rather than assuming that all revenue from the entire product results from the patented feature.

The entire market value rule (EMVR) is an exception to the general requirement that damages be apportioned to the value attributable to the patented technology. Under the rule, damages may, in appropriate circumstances, be based on the entire value of a multi-component product when the patented feature drives consumer demand for the entire product.The rule is applied narrowly and requires evidence establishing the necessary connection between the patented feature and demand for the complete product. The mere fact that the patented feature is important, commercially successful, or incorporated into the product does not automatically justify using the entire product's sales as the royalty base. Where the patented feature does not drive demand for the whole product, an appropriately apportioned royalty base is generally required.

Lost profits attempt to determine the profits the patent owner would have earned but for the infringement. The analysis generally compares the actual economic outcome during the infringement period with the outcome that would reasonably have occurred in a counterfactual world without the infringement.The calculation may consider lost sales, price erosion, lost opportunities, and other proven economic effects. A common framework is the Panduit test, which examines whether demand existed for the patented product, whether acceptable non-infringing substitutes were unavailable, whether the patent owner had sufficient manufacturing or sales capacity, and the amount of profit that would have been earned on the additional sales.The analysis must establish a causal connection between the infringement and the claimed loss. Simply showing that the infringer sold products while the patent owner also sold products is not sufficient to establish lost profits.

The Panduit test is a commonly used framework for establishing entitlement to lost profits. It asks whether the evidence supports four basic conditions:Demand: There was demand for the patented product.Absence of acceptable non-infringing substitutes: Customers did not have acceptable alternatives that would have satisfied the relevant demand.Manufacturing and marketing capacity: The patent owner had sufficient capacity to exploit the additional demand.Profit: The amount of profit that would have been earned on the additional sales can be established.If these conditions are supported, the analysis can estimate the sales the patent owner would likely have made absent infringement and the corresponding lost profit per unit. The test is an evidentiary framework rather than an automatic formula, and other economic evidence may also be relevant depending on the circumstances.

Future revenues should be projected using reasonable, evidence-based assumptions about the expected sales, prices, market growth, product life cycle, and competitive environment. Historical sales data can provide a starting point, but the projection should account for known changes in market conditions, product adoption, competition, and technological developments.The projection should also distinguish between revenue attributable to the accused product and revenue attributable to the patented technology where apportionment is required. Assumptions should be explicitly documented and tested against available historical and market evidence. Overly optimistic growth assumptions unsupported by contemporaneous evidence can substantially overstate damages.

Discounting converts future monetary amounts into their present value, recognizing that a dollar received in the future is worth less than a dollar received today because of the time value of money and associated risk. In a patent damages model involving future losses or royalties, projected amounts are therefore discounted to the appropriate valuation date.A simplified present-value calculation is:Present Value = Future Cash Flow ÷ (1 + discount rate)ᵗwhere t represents the number of periods until the cash flow is received. The appropriate discount rate should reflect the relevant economic risk and the nature of the projected cash flows. Discounting should be applied consistently with the assumptions used elsewhere in the damages model so that risk is not inadvertently counted twice.

Weighted Average Cost of Capital (WACC) represents a company's blended cost of financing from debt and equity and can be used as a discount rate when the projected cash flows have a risk profile appropriately reflected by the company's overall cost of capital. It is calculated by weighting the cost of debt and cost of equity according to their respective proportions in the company's capital structure.In patent damages, WACC may therefore be relevant when converting projected future revenues, profits, or royalty payments into present value. However, it should not automatically be used simply because it is readily available. The discount rate must correspond to the risk characteristics of the specific cash flows being valued. Using a company-wide WACC for a significantly different, project-specific risk can overstate or understate damages.

Year-by-year damages are calculated by determining the appropriate damages amount for each infringement period, rather than applying one aggregate figure across the entire period. For each year, the analyst identifies the relevant infringing sales or lost sales, applicable prices and margins, royalty base, royalty rate, and any other damages components supported by the evidence.A simplified reasonable-royalty model would be:YearInfringing SalesRoyalty RateAnnual RoyaltyYear 1$10M2%$200KYear 2$15M2%$300KYear 3$20M2.5%$500KThe annual amounts are then aggregated and, where appropriate, adjusted for interest, discounting, changes in royalty rates, product mix, or other time-dependent factors. The model should preserve the underlying assumptions for each year so that the damages calculation can be traced back to actual sales and economic evidence rather than appearing as a single unsupported total.