SD Card Capacity Calculator

Pick your card and your recording settings — find out how much video time fits, the data rate, and the minimum card class you need to avoid dropped frames.

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Your shoot

Card capacity
Resolution
Frame rate (fps)
Recording time that fits
0
—
0MB/s data rate
—minimum class required
0GB / minute
0total minutes
Time per card
Quick scenarios
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0 MB/s · —

How SD card capacity is calculated

The time a card holds is its usable capacity divided by how fast the camera writes data:

Time = usable capacity (MB)data rate (MB/s)

The usable capacity is the labelled size minus the ~7% lost to formatting (a 128 GB card is ~119 GB real). The data rate (MB/s) is set by your resolution, frame rate and codec — the higher they are, the more megabytes per second and the less time fits. Divide one by the other and you get the duration. We also tell you the minimum card class you need: if your card is slower than that data rate, recording stops or drops frames.

Example: how much 4K video fits on 128 GB

You have a 128 GB card and shoot 4K UHD at 30 fps in H.265:

  • 128 GB × 0.93 ≈ 119 GB usable.
  • 4K30 in H.265 = 200 Mbps = 25 MB/s data rate.
  • 119,000 MB ÷ 25 MB/s ≈ 4,760 s ≈ 1 h 19 min of recording.
  • Minimum class: a V30 card is enough for that data rate.

Switch the codec to ProRes 422 HQ (110 MB/s) and the same card drops to about 18 minutes — and that data rate is beyond SD-card limits: you'd need CFexpress Type A or an external SSD.

SD card capacity FAQ

How much video fits on a 128 GB card?
It depends on resolution, frame rate and codec. At 4K 30 fps in H.265 (~7 MB/s) you get around 4-5 hours; in ProRes or RAW it is only minutes. Enter your settings and the calculator gives the exact time.
Why is the usable capacity smaller than the labelled size?
Formatting and the file system use about 7%, so a 128 GB card gives ~119 GB of real space. The calculator already accounts for that.
What card class do I need so recording does not drop?
The minimum class depends on the data rate (MB/s), not the card size. The calculator shows the exact class — V30, V60, V90 or, for high data rates, CFexpress / SSD.
Does it also work for CFexpress and SSDs?
Yes. When the data rate exceeds what an SD card can sustain, the tool recommends CFexpress Type A, CFexpress Type B or a high-performance SSD.
Are the times exact?
They are estimates based on typical average bitrates per codec. Real time varies a little with scene complexity, so leave ~10-15% headroom.