Check if an unlimited plan is worth it.
An unlimited plan is worth buying only above a specific usage threshold, and that threshold is calculable: it is the included allowance plus the price premium divided by the overage rate. Below it the metered plan is cheaper; above it the overage charges overtake the premium. Comparing your actual usage with that break-even point turns a marketing question into an arithmetic one.
Break-even usage for unlimited
Metered cost = base + max(0, usage - included) x overage rate; break-even GB = included + (unlimited price - base) / overage rate; saving = metered cost - unlimited price
Rarely. Most plans apply a deprioritisation threshold — often 30-100 GB — beyond which your traffic is slowed during congestion, and tethering usually has a separate hard allowance. Read the fair use terms before treating capacity as unbounded.
Your worst realistic month, if overage is uncapped. The value of unlimited is partly insurance against a single expensive month, which an average-based comparison misses entirely.
Then the metered plan's downside is bounded and the comparison becomes purely about the average. Substitute the capped maximum for the computed metered cost when your usage would exceed it.