Photography Calculators
SD Card Capacity Calculator
https://www.photosizing.com/calculators/sd-card-capacity/
Estimate only — not a light meter, a shooting prescription or a studio plot. Confirm on a test shot.
SD Card Capacity Calculator
Cards are sold in decimal gigabytes. Stills count is floor of (GB × 1000 / file MB). Video minutes are (GB × 8000 / Mbps) / 60 if you set a bitrate; leave bitrate at 0 for stills only. Format in the camera, leave a margin, and do not start a ceremony on the last 4 GB. A test burst of 20 RAWs tells you the real file size better than the brochure.
Inputs
Results
- Stills that fit
- 2,844
- Video that fits
- 85.3min
Whole files of the average size that fit on the labelled GB.
Zero if bitrate is 0.
The Result is indicative and educational. It does not constitute a design, a technical opinion or medical advice and does not replace calculations or verification by a person with the appropriate qualifications and authorisations. Before purchase, installation or use in practice – in particular in electrical installations – the Result should be verified by a qualified specialist. Details: Terms of Service, point 4.
Example products
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128 GB SD card
A labelled 128 GB card is the default in this math. Buy two; format both in the body.
Typical range: $15–$40
CFexpress card
Same GB math, faster writes. Use this size estimate, then buy CFexpress if the codec needs the speed.
Typical range: $80–$250
Camera backpack
Spare cards live in a pocket you can reach, not the bottom of a suitcase. Label them shot/empty.
Typical range: $80–$300
Calculation method
Treat 1 GB as 1000 MB. Still count is the whole number of files of your average size that fit. Video minutes convert bits on the card to time: capacityGB × 8e9 bits, divided by bitrate Mbps × 1e6, then by 60 (equivalently GB×8000/Mbps/60). Zero if you set bitrate to 0. A 128 GB card at 45 MB RAWs is 2844 stills; at 200 Mbps that is about 85 minutes of video. Containers, dual-slot mirroring and the camera’s reserve are not subtracted.
Exact formula
stillCount = floor(capacityGB×1000 / fileSizeMB). videoMinutes = capacityGB×8000 / bitrateMbps / 60 if bitrate>0 else 0. Limits: Decimal GB (1000, not GiB); camera overhead, dual-slot mirroring, format waste, audio mux and VBR omitted — real minutes run shorter.
Speed class
Capacity is not sustain rate. V30/V60/V90 and CFexpress ratings are about dropped frames, not how many JPEGs fit.
Format in camera
A card formatted on a PC can still throw ‘cannot record’. Format in the body you will shoot, every job.
Frequently asked questions
Why does the computer show 119 GB?
Windows counts in 1024s and still calls it GB: 128 × 10⁹ bytes is 119.2 GiB. The label counts in 1000s, and so does macOS Finder. This calculator follows the label so it matches the shop sticker.
RAW+JPEG?
Add the two sizes for file size, or you will count twice as many frames as you can actually shoot.
Dual slot backup?
If slot 2 mirrors slot 1, you do not get extra capacity. If it overflows, you do. Set the camera mode before you trust this number.
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