Memory Card FAQ
General card questions. Looking for a specific capacity? See 128GB, 256GB or the calculator.
Why does my card show less space than advertised?
Card makers count in decimal gigabytes (1GB = 1,000,000,000 bytes) while computers count in binary, and formatting reserves some space. Expect roughly 93% of the advertised size to be usable — a '128GB' card gives you about 119GB.
Do photo counts differ between SD, microSD and CFexpress?
No — capacity is capacity. The card format changes speed and durability, not how many photos fit.
What card speed do I need?
For stills, almost any modern card works. For 4K video look for U3 / V30 or better; for 8K or high-bitrate recording, V60/V90 or CFexpress.
Should I buy one big card or several smaller ones?
Working photographers usually prefer two medium cards over one giant one — a failed 128GB card loses half as much as a failed 256GB. Many cameras can also write backups to a second slot.
Are these numbers exact?
No — they're planning estimates. File size varies with scene detail, ISO noise, compression settings and codec. The calculator's assumptions are documented on the About page.