About the Memory Card Capacity Calculator
This memory card capacity calculator estimates how many photos, or how many minutes of video, fit on an SD, microSD or CFexpress card. Choose the card size, enter the average size of one photo and your video bitrate, and it shows the shot count and recording time for your card plus a quick comparison table for every common card size from 16 GB to 1 TB.
Use it before a trip, a wedding or a shoot day to decide how many cards to pack, when choosing between raw and JPEG, or when picking a video codec and resolution that will fit your storage. Drone pilots, vloggers and dash-cam users can use the video side to see how long they can record before swapping cards.
Cards are sold in decimal gigabytes (1 GB = 1,000,000,000 bytes), which is why a computer that counts in binary GiB shows a 128 GB card as about 119 GB — no space is actually missing. A small allowance is subtracted for the file system. Photo sizes vary with scene detail and ISO, so use an average from your own camera if you can; video bitrate is shown in your camera’s menu or manual.
How to use the memory card capacity calculator
- 1Choose whether you mainly shoot photos or video and pick the card size.
- 2Enter the average size of one photo from your camera.
- 3Enter the video bitrate for your resolution and codec.
- 4Leave the file-system allowance at 1% unless you know otherwise.
- 5Read how many photos or minutes fit, and compare card sizes in the table.
Formula and method
Card capacity is converted to bytes using decimal gigabytes, as printed on the card, and a small allowance is removed for the file system. The number of photos is the usable bytes divided by the average photo size, rounded down to whole files.
Video bitrate is quoted in megabits per second, and there are 8 bits in a byte, so recording time is usable bytes × 8 divided by the bitrate in bits per second. Variable-bitrate codecs average below their peak, so real recording times are often a little longer for H.264/H.265 and almost exact for constant-bitrate formats such as ProRes or All-Intra.
- capacity
- Card size in decimal GB
- allowance
- File-system/format allowance (fraction)
- photo MB
- Average file size of one photo (decimal MB)
- Mbps
- Video bitrate in megabits per second
Worked examples
128 GB card with 25 MB raw files
After a 1% allowance a 128 GB card has 126.72 GB free. Dividing by 25 MB per raw file gives 5,068 photos. The same card would hold 126.72 × 8,000 ÷ 100 = 10,138 seconds, or about 169 minutes, of 100 Mbps video.
How many JPEGs on a 64 GB card?
64 GB minus 1% is 63.36 GB, or about 59 GiB as a computer reports it. At 8 MB per JPEG that is 7,920 photos.
4K video at 150 Mbps on a 256 GB card
A 256 GB card has 253.44 GB usable. At 150 Mbps the camera writes 18.75 MB per second, so the card lasts 253.44 × 8,000 ÷ 150 = 13,517 seconds — about 3 hours 45 minutes of 4K footage.
1 TB CFexpress card with 400 Mbps All-Intra
A 1 TB card is 1,000 decimal GB; 1% off leaves 990 GB. At 400 Mbps the camera writes 50 MB per second, so the card records 990 × 8,000 ÷ 400 = 19,800 seconds — 5 hours 30 minutes.
Frequently asked questions
How many photos can a 64 GB card hold?+
It depends on file size. With 25 MB raw files from a 24 MP camera, a 64 GB card holds about 2,500 photos; with 8 MB JPEGs about 7,900; with 60 MB raw files from a 45 MP camera only about 1,050.
How many minutes of 4K video fit on a 128 GB card?+
At a typical 100 Mbps 4K bitrate, a 128 GB card records roughly 2 hours 50 minutes. At 150 Mbps it is about 1 hour 50 minutes, and at 400 Mbps (All-Intra) around 40 minutes.
Why does my 128 GB card show only 119 GB?+
Card makers count 1 GB as 1,000,000,000 bytes, but most operating systems count in binary units of 1,073,741,824 bytes while still labelling them GB. 128 billion bytes is 119.2 GiB, so nothing is missing — the units are different.
What card speed do I need for video?+
The card’s minimum sustained write speed must exceed your bitrate divided by 8. 100 Mbps needs 12.5 MB/s, so a V30 (30 MB/s) card is fine; 400 Mbps needs 50 MB/s, so use V60 or V90 SD cards or CFexpress.
Is it better to use one big card or several smaller ones?+
Several smaller cards limit how much you lose if one fails or is lost, while one large card means fewer swaps during long video takes. Many professionals use dual card slots to record a backup copy at the same time.