TF Card Capacity Estimator
Enter your recording parameters and get an estimated capacity range. The same camera at 4K and at 1080p, or set to loop recording versus kept for 30 days, needs very different cards — so the tool asks for the workload, not a fixed number.
How the estimate is built
Data per hour (GB) = bitrate (Mbps) × 3600 ÷ 8 ÷ 1024.
Total data (GB) = data per hour × recording hours per day × retention window (days). With loop recording, the window is one overwrite cycle; without it, the full number of days you keep footage.
With margin = total data × (1 + margin%).
The suggested card size rounds up to a standard capacity (16 / 32 / 64 / 128 / 256 / 512 GB).
Limitations
- This is a planning aid, not a guarantee. Real usage varies with codec, bitrate fluctuation, file-system overhead and how the device writes.
- The file system matters: cards above 32 GB are typically SDXC and use exFAT; some older hosts only read FAT32 and will not see a larger card.
- Sustained write, not peak read, is what continuous recording needs. Capacity alone does not prove the card can hold a 24/7 write loop.
- Confirm the capacity and speed against your actual device before ordering volume.
Sources
- SD Association — Capacity (SD/SDHC/SDXC/SDUC)
SDHC spans more than 2GB up to 32GB and uses the FAT32 file system; SDXC spans more than 32GB up to 2TB and uses exFAT. Speed grades cover C2/C4/C6/C10, UHS U1/U3, and Video Speed Class V6/V10/V30/V60/V90.
- Microsoft — Microsoft exFAT technology licensing
exFAT is a Microsoft-patented file system that allows single files larger than 4GB (the FAT32 limit); the SD Association adopted exFAT for high-capacity, high-speed SDXC / SDUC cards.
- Microsoft — Azure RTOS FileX User Guide — exFAT / FAT32
FAT32 caps a single file at 4GB and by default addresses storage media up to 32GB; exFAT allows single files of roughly 1 EB; flash / SD cards above 32GB require exFAT.
External sources explain industry standards and are accessed on 2026-10-18. They describe the standard, not WINTEL product parameters.
Related: U1 vs U3 vs V30, TF card RFQ checklist, request a quote.
Frequently asked questions
How does the estimator arrive at a capacity?
It multiplies bitrate by recording hours to get data per hour, totals it over the retention period you want, then adds a margin for file system overhead and fragmentation. The margin is the part most buyers skip, and it is why a card that looks big enough fills up early.
Why add a margin on top of the raw total?
Because a card is never empty in normal use. File system structures, deleted-but-not-overwritten data and recording overhead all consume space, and a card that runs close to full slows down and wears faster. The margin is headroom, not padding.
Does a larger card always solve a capacity problem?
No. If the device overwrites in a loop, a larger card mainly extends the rewrite interval, which helps endurance. If the device writes sequentially and never deletes, a larger card only delays the point where someone has to retrieve the data.