Data Cap Overage Cost Calculator
Overage fees are designed to surprise you on the bill. Enter your plan's cap, how far you are into the billing cycle, and how much you've used so far to see the number before the cycle ends. Nothing uploaded.
Projection
-Full breakdown
Learn more: projecting data overage cost
The projection is a straight-line pace, not a forecast
The calculator divides the data you have used by the days elapsed in the cycle to get a daily pace, then multiplies that pace across the full length of the cycle. The figures the page opens with show it: 20GB used in the first 10 days of a 30-day cycle is 2GB a day, which projects to 60GB by the closing date.
Overage is whatever that projection exceeds your cap, floored at zero, so a projection landing under the cap shows no cost rather than a credit. Against the 50GB cap in the same example that leaves 10GB of overage, which at $10 a gigabyte comes to $100.
Because the pace is an average of the days so far, it is at its shakiest at the start of a cycle and firms up as the cycle runs on. A single heavy evening in the first three days can double the projected total on its own.
Per-GB and per-block pricing are different shapes of cost
A per-gigabyte rate scales smoothly, adding the same amount for every extra gigabyte. A per-block rate rounds the overage up to the next whole block, so the cost climbs in steps and sits flat in between.
With 5GB blocks at $10 each, an 11GB overage and a 15GB overage both cost $30, since both round up to three blocks. One more gigabyte past that 15 tips into a fourth block and $40. The same 10GB overage from the example above costs $100 under a $10/GB rate but $20 as two blocks.
That is worth checking before you assume block pricing is the expensive option. Which way it falls depends entirely on the price per block against the size of the block, and the two modes on this page take those numbers straight from you rather than from any carrier list.
Mobile Internet Resource Center's directory of unlimited cellular data plans points at a related trap worth budgeting around: most unlimited smartphone plans cap high-speed hotspot and tethering data separately from on-device data, and once that smaller pool runs out the tethered connection is slowed to near-unusable speeds or switched off while the phone itself carries on at full speed.
FAQ
Why does my projected total swing so much early in the cycle?
The pace is usage divided by days elapsed, so two or three days of data give it very little to average over. One heavy day early on moves the projection far more than the same day would in week three.
Does throttling count as an overage here?
No. This tool models the money side only, so a plan that slows you down instead of billing you shows no projected cost even when you are heading well past the cap. Check which of the two your plan does before reading a $0 result as good news.
What should I put in the block size and price fields?
Take both from your own plan's terms rather than the defaults, which are only a common shape of pricing. Carriers vary the block size and its price independently, and that pairing is what decides whether a small overage costs a little or a lot.