Card size is only one part of recording time. Bitrate, motion frequency, resolution and whether the camera records continuously can change retention dramatically.
Why two cameras use storage differently
Video is stored as compressed data. A higher bitrate writes more data every second, while motion-only recording writes data only when activity is detected. A busy shop entrance can therefore fill the same card much faster than a quiet storeroom.
Resolution alone does not determine storage use. Encoding, frame rate, night scenes and the amount of movement also matter. Treat any day estimate as a planning range rather than a guarantee.
A simple way to choose capacity
Begin with how many days of local footage you want available, then adjust for how active the scene is.
- 64GB: short retention or lower-activity locations
- 128GB: a balanced starting point for many homes and small shops
- 256GB: longer retention when the exact camera supports the card
- Continuous recording: plan for much higher daily storage than motion-only recording
Compatibility matters more than maximum size
Never assume every camera accepts every SD card capacity. Check the model specification and use a compatible card type and speed. A card that is too large, damaged or formatted incorrectly may not be detected or may fail to record reliably.
After installation, confirm that recording is enabled, set the correct recording mode, format the card through the supported app when instructed, and play back a short test clip.
Storage setup checklist
Complete a real playback test before relying on the camera for important footage.
- Confirm the model's supported maximum capacity
- Use a suitable card from a reliable source
- Select continuous or event recording
- Enable overwrite/loop recording if supported
- Check the date, time and playback after installation
Compare the models that fit your site
Choose the connection and power first, then compare coverage and functions.