Estimate data used uploading photos.
Automatic photo backup is the largest source of upstream traffic on most phones, and file sizes have grown sharply: a modern 48-megapixel HEIC frame is 3-6 MB and a ProRAW capture can exceed 25 MB. Adding a modest allowance for protocol overhead and failed retries gives a realistic figure, and the photos-per-gigabyte number makes the trade-off between capture format and plan size concrete.
Photo backup volume
Effective size = file size x (1 + overhead); monthly GB = photos per day x effective size x days / 1024; photos per GB = 1024 / effective size
A 12-megapixel HEIC is about 2-3 MB, a 48-megapixel HEIC 3-6 MB, the same shot as JPEG roughly 50 percent larger, and ProRAW or RAW 25-80 MB. Live Photos and burst sequences multiply the count considerably.
Entirely, if backup is set to wifi only. That single setting is the most effective mobile data saving available on a phone, because photo backup otherwise runs continuously in the background.
Because measured upload traffic consistently exceeds the sum of file sizes. TLS and HTTP framing, metadata, thumbnail generation and interrupted uploads that restart typically add 5-10 percent.