Memory Card Photo Capacity Calculator
Enter your card size and measured photo file sizes to estimate photos per card, cards required for a shoot, and the storage margin left on one card.
Photos per card2,596
- Cards required
- 1
- Will the target shoot fit on one card?
- Yes
- One-card surplus or shortfall (GB)
- 4.06
- Target card utilization
- 96.28%
- Storage per shutter press (MB)
- 43
Capacity is calculated with 1 GB equal to 1,024 MB after the usable-capacity adjustment.
Negative surplus means the target shoot needs more than one card or larger cards.
How to use this calculator
- Enter the advertised capacity printed on one card.
- Keep the usable-capacity default unless your camera or computer shows a better figure.
- Enter the average primary file size, and add the companion JPEG size if you shoot RAW plus JPEG.
- Reserve storage for video, existing files, or an intentional buffer.
- Enter the expected shutter count to see whether one card is enough.
How photo capacity is calculated
A memory card's printed capacity is usually a decimal storage label, while cameras and computers often report space in binary units. Formatting also uses a little space. This calculator starts with the advertised card size, applies the usable-capacity percentage, subtracts any reserved storage, and then divides the remaining space by the file size created by each shutter press.
The formula is:
U = max(0, C * 1024 * A / 100 - R * 1024)
F = P + J
N = floor(U / F)
K = ceil(T / N), when the target is above zero and at least one photo fits on a card.
- C is the advertised card capacity in GB.
- A is the usable-capacity percentage.
- R is storage reserved for video or other files in GB.
- P is the average RAW or primary file size in MB.
- J is the average companion JPEG or sidecar file size in MB.
- T is the target shutter count for the shoot.
What changes the estimate most
The biggest driver is the combined file size per shutter press. A camera that averages 43 MB per RAW plus JPEG pair stores far fewer photos than one that averages 24 MB, even on the same card. The best input is not the camera's megapixel count. It is the average of real files from the same camera, image quality setting, bit depth, and compression mode you plan to use.
Reserved storage matters when the card will also hold video clips or when you want an intentional buffer. A 128 GB card with 10 GB reserved gives up space for hundreds of still photos before the still-photo calculation even begins.
What this calculator leaves out
The result is a planning estimate, not a camera guarantee. Compressed RAW and JPEG sizes change with scene detail, ISO noise, manufacturer compression, and whether the camera stores embedded previews. The calculator also does not model write speed, burst-buffer limits, card wear, corruption risk, or dual-slot backup recording. For paid work, many photographers carry more cards than the arithmetic requires so that a single card is not the only copy of a whole event.
Worked example
Suppose one 128 GB card has 93% usable capacity, 10 GB is reserved for video, each RAW file averages 35 MB, and each companion JPEG averages 8 MB. Usable still-photo storage is 128 * 1024 * 93 / 100 - 10 * 1024 = 111,656.96 MB. Each shutter press uses 35 + 8 = 43 MB, so the card holds floor(111,656.96 / 43) = 2,596 photos.
For a target of 2,500 photos, one card is enough. The target uses 107,500 MB, leaving about 4.06 GB on that card, or 96.28% utilization.
Common questions
How many RAW photos can a 64 GB, 128 GB, or 256 GB card hold?
It depends on the average RAW file size from your camera. With 93% usable capacity and no reserved space, a 35 MB average RAW file gives about 1,740 photos on 64 GB, 3,481 on 128 GB, and 6,962 on 256 GB. Larger compressed RAW files reduce those counts in direct proportion.
Why does a formatted card show less space than its advertised capacity?
Storage labels use decimal GB, while many devices report binary units that are based on 1,024 MB per GB. File-system formatting and camera folders also consume some space. The usable-capacity field lets you use the camera's displayed capacity when you know it.
How do I find my camera average RAW or JPEG file size?
Shoot a representative set of photos using the same quality settings you plan to use. Check the file sizes on a computer, add them, and divide by the number of files. A sample that includes bright, dark, detailed, and high-ISO scenes is more useful than one test image.
How should RAW plus JPEG shooting be calculated?
Enter the RAW file size as the primary file size and the JPEG file size as the companion file size. The calculator adds them because each shutter press stores both files. If you shoot only RAW or only JPEG, enter zero for the companion file size.
Does card speed change how many photos fit?
No. Speed affects how quickly the card can write data and clear the camera buffer, not how much data the card can store. Capacity, usable space, and file size determine the photo count.