Estimate how many photos a memory card can hold from card capacity, image resolution and file format.
RAW 通常 20–50 MB，JPEG 较小。
⚠️ Unit-basis notice: this page uses the card-vendor basis of 1 GB = 1000 MB (decimal), while photo file sizes estimated on a binary basis (1 MB = 1024×1024 bytes, MiB) differ by about 7.4%. When cross-checking "file size × shots" against card capacity across pages, convert to the same basis first.
| Item | Formula / Rule | Source / Standard |
|---|---|---|
| Frame count | Frames = ⌊usable capacity ÷ per-frame size⌋, with usable capacity at 93% of nominal | SD Association, SD Specifications Part 1 Physical Layer |
| Per-frame size | Per frame = pixels × bit depth ÷ 8 × compression factor, typically 0.5 to 1.0 for RAW | SD Association, SD Specifications Part 1 Physical Layer |
| Filesystem overhead | FAT32 and exFAT cluster and directory overhead costs roughly 3% to 7% of capacity | ISO/IEC 9293 FAT file system specification |