What correct compression depth for CPR adult?

For effective adult CPR, the compression depth should be at least 5 centimeters (2 inches), but not exceeding 6 centimeters (2.4 inches), as measured over the adult sternum. It's measured from the center of the chest in between the nipples to the depth. Compressing the chest beyond this depth may increase the risk of serious complications, such as rib fractures. It's recommended to let the chest fully recoil between each compression to enable proper blood flow during chest compressions.