Identify your use-case: grating over pasta, melting in a bake, or slicing for a board/sandwich.
Choose the closest match: Parmesan/Grana for grating, Asiago for firm melt, Swiss/Gouda for sandwich-style melting.
Swap by the listed ratio. If your substitute is sharper (like Pecorino), reduce any added salt by about ¼.
For smoother melt/grate performance, grate harder cheeses finely and stir them in during the last 1–2 minutes of heat.
Taste and adjust with pepper, a pinch of acid (lemon/vinegar) for tang, or a small drizzle of butter/oil for roundness.