X0609 4 2026-05-13 0 0001315257 Koppers Holdings Inc. KOP 0001229771 BALL M LEROY false 436 SEVENTH AVENUE PITTSBURGH PA 15219 1 1 0 0 CEO 0 Common Stock 2026-05-13 4 S 0 2659 42.55 D 444096.4007 D Includes 496 shares of Koppers Holdings Inc. common stock acquired pursuant to the Koppers Holdings Inc. Employee Stock Purchase Plan on March 31, 2026. These acquisitions were exempt under both Rule 16b-3(c) and Rule 16b-3(d). /s/ Stephanie L. Apostolou, Attorney in Fact 2026-05-14