The expressions ともなると and にもなると are used to convey the idea that once something reaches a certain level, status, or stage, a natural or expected consequence follows. They emphasize that when a situation involves something of notable significance – a high rank, a special occasion, an advanced stage – the result is naturally different from ordinary circumstances.
These patterns often translate to "once you're talking about…", "when it comes to (something of that level)", or "once it reaches the point of…" in English.
The most common usage attaches ともなると or にもなると directly to a noun representing a notable status, position, time period, or quantity.
Both forms highlight that crossing a particular threshold naturally brings about a certain outcome. The speaker treats the result as expected or unsurprising given the level involved.
The two forms are largely interchangeable. ともなると is slightly more common in formal or written contexts, while にもなると can feel marginally more conversational and often emphasizes the idea of "even reaching" that level. In practice, the difference is subtle.
The simpler form ~となると means "when it comes to…" or "if it turns out that…" and is used more broadly. ともなると / にもなると carry the added nuance that the topic is something remarkable or of a high degree, making the consequence feel natural or inevitable.