Check your plan against data caps.
Overage is rarely billed per gigabyte. Most providers charge in blocks — commonly 50 GB for a fixed fee — and round up, so exceeding a cap by a single gigabyte costs the same as exceeding it by fifty. Computing the number of blocks rather than a per-gigabyte rate gives the real charge, and shows why sitting just above a block boundary is the worst place to be.
Block-based overage charging
Overage GB = usage - cap; blocks = ceiling(overage / block size); charge = blocks x block price
Caps of 1-1.2 TB are common in North America, with overage around 10 to 15 currency units per 50 GB block and a monthly cap on total overage charges. Many providers also sell an unlimited add-on for a flat monthly fee.
Divide the add-on price by the block price. If you routinely exceed the cap by more than that many blocks, the add-on is cheaper — and it also removes the risk of an unusually heavy month.
Almost always the cap is combined upstream and downstream. That surprises households running cloud backup or uploading video, where upstream can be the larger contribution.