X0508 4 2025-12-16 0 0001315257 Koppers Holdings Inc. KOP 0001450800 Sullivan James A. 436 SEVENTH AVENUE PITTSBURGH PA 15219 0 1 0 0 President and CTO 0 Dividend Equivalent Rights 2025-12-16 4 A 0 522 0 A Common Stock 522 809 D The dividend equivalent rights ("DERs") accrued with respect to additional time-based and performance-based restricted stock units ("RSUs" and "PSUs", respectively) credited to the reporting person. Of this total, 420 DERs accrued with respect to RSUs granted on January 4, 2022, January 4, 2023, January 4, 2024, and January 3, 2025 and 102 DERs accrued with respect to PSUs granted on January 4, 2023. Each DER is the economic equivalent of one share of Koppers Holdings Inc. common stock. /s/ Stephanie L. Apostolou, Attorney in Fact 2025-12-17