When a tactical naval victory becomes strategic

At what point does a tactical victory at sea become an overall strategic victory?

When it lets you carry out your maritime strategy with a strong chance that the enemy cannot or will not interfere effectively.

The transition from tactical to strategic victory depends on operational effect rather than on the number of ships damaged. A naval victory has strategic weight when it enables the victor's wider maritime strategy. The enemy must either choose not to interfere or lose the practical ability to do so. Taranto mattered because it reduced Italian freedom of action and changed British force requirements beyond the harbour itself.