RAMBUS INC Stock Compensation Disclosure

14. Equity Incentive Plans and Stock-Based Compensation

Equity Incentive Plans

The Company has two equity incentive plans under which grants are currently outstanding: the 2015 Equity Incentive Plan (the “2015 Plan”) and the 2019 Inducement Equity Incentive Plan (the “2019 Inducement Plan”). The 2015 Plan and 2019 Inducement Plan were the Company’s only plans for providing stock-based incentive awards to eligible employees, executive officers, non-employee directors and consultants as of December 31, 2025. Grants under all plans typically have a requisite service period of 48 months, have straight-line vesting schedules and expire not more than 10 years from date of grant.

General Stock Option Information

Employee Stock Purchase Plan

During the years ended December 31, 2025, 2024 and 2023, the Company had one employee stock purchase plan, the 2015 Employee Stock Purchase Plan (“2015 ESPP”). Employees generally will be eligible to participate in the plan if they are employed by the Company for more than 20 hours per week and more than five months in a calendar year. The 2015 ESPP provides for six-month offering periods, with a new offering period commencing on the first trading day on or after May 1 and November 1 of each year. Under the plan, employees may purchase stock at the lower of 85% of the fair market value of the Company’s common stock at the beginning of the offering period (the enrollment date) or the end of each offering period (the purchase date). Employees generally may not purchase more than the number of shares having a value greater than $25,000 in any calendar year, as measured at the purchase date.

The Company issued 166,458 shares at an average price of $41.12 per share during the year ended December 31, 2025. The Company issued 119,350 shares at an average price of $43.14 per share during the year ended December 31, 2024. The Company issued 172,711 shares at an average price of $31.10 per share during the year ended December 31, 2023. As of December 31, 2025, 2.1 million shares under the 2015 ESPP remained available for issuance.

Stock-Based Compensation

Stock Options

There were no stock options granted during the years ended December 31, 2025, 2024 and 2023, respectively.

As of December 31, 2023, all compensation cost net of expected forfeitures, related to unvested stock-based compensation arrangements granted under the stock option plans had been fully recognized. As a result, there was no stock-based compensation expense related to stock options for the years ended December 31, 2025 and 2024. Stock-based compensation expense related to stock options was immaterial for the year ended December 31, 2023.

The total fair value of options vested for the year ended December 31, 2023 was $0.5 million.

Employee Stock Purchase Plan

For the years ended December 31, 2025, 2024 and 2023, the Company recorded stock-based compensation expenses related to the 2015 ESPP of $2.7 million, $1.9 million and $1.8 million, respectively.

As of December 31, 2025, there was $1.4 million of total unrecognized compensation cost related to stock-based compensation arrangements granted under the 2015 ESPP. That cost is expected to be recognized over four months.

Valuation Assumptions

The Company estimates the fair value of stock awards using the Black-Scholes-Merton model (“BSM model”). The BSM model determines the fair value of stock-based compensation and is affected by the Company’s stock price on the date of the grant, as well as assumptions regarding a number of highly complex and subjective variables. These variables include expected volatility, expected life of the award, expected dividend rate and expected risk-free rate of return. The assumptions for expected volatility and expected life are the two assumptions that significantly affect the grant-date fair value. If actual results differ significantly from these estimates, stock-based compensation expense and the Company’s results of operations could be materially impacted.

The fair value of stock awards is estimated as of the grant date using the BSM option-pricing model assuming a dividend yield of 0% and the additional weighted-average assumptions as listed in the table below.

Expected Stock Price Volatility: Given the volume of market activity in its market traded options, the Company determined that it would use the implied volatility of its nearest-to-the-money traded options. The Company believes that the use of implied volatility is more reflective of market conditions and a better indicator of expected volatility than historical volatility. If there is not sufficient volume in its market traded options, the Company will use an equally weighted blend of historical and implied volatility.

Risk-free Interest Rate: The Company bases the risk-free interest rate used in the BSM valuation method on implied yield currently available on the U.S. Treasury zero-coupon issues with an equivalent term. Where the expected terms of the Company’s stock-based awards do not correspond with the terms for which interest rates are quoted, the Company uses an approximation based on rates on the closest term currently available.

Expected Term: The expected term of options granted represents the period of time that options granted are expected to be outstanding. The expected term was determined based on historical experience of similar awards, giving consideration to the contractual terms of the stock-based awards, vesting schedules and expectations of future employee behavior. The expected term of ESPP grants is based upon the length of each respective purchase period.

Nonvested Equity Stock and Stock Units

The Company grants nonvested equity stock units to officers, employees and directors. For each of the years ended December 31, 2025, 2024 and 2023, the Company granted nonvested equity stock units totaling 1.3 million. These awards have a service condition, generally a service period of four years, except in the case of grants to directors, for which the service period is one year. For the years ended December 31, 2025, 2024 and 2023, the nonvested equity stock units were valued at the date of grant, giving them a fair value of approximately $70.4 million, $74.8 million and $60.7 million, respectively. During the years ended December 31, 2025, 2024 and 2023, the Company granted performance unit awards to certain Company executive officers with vesting subject to the achievement of certain performance and/or market conditions. The ultimate number of performance units that can be earned can range from 0% to 200% of target depending on performance relative to target over the applicable period. The shares earned will vest on the third anniversary of the date of grant. The Company’s shares available for grant have been reduced to reflect the shares that could be earned at the maximum target.

For the years ended December 31, 2025, 2024 and 2023, the Company recorded stock-based compensation expense of approximately $51.5 million, $43.0 million and $43.1 million, respectively, related to all outstanding nonvested equity stock grants.

Unrecognized compensation cost related to all nonvested equity stock grants, net of estimated forfeitures, was approximately $87.4 million as of December 31, 2025. This amount is expected to be recognized over a weighted-average period of 2.0 years.