Which Memory Card for a Dash Cam? Size, Speed Class and Endurance

A dash cam overwrites its card continuously, hour after hour. Ordinary cards are built for phones and cameras that write occasionally; under constant rewriting they wear out within months, often silently, so the camera appears to work but saves corrupted files. High-endurance cards are rated for many thousands of hours of continuous recording.

Recording time is approximate: it depends on the bitrate and on H.264 versus H.265 compression, which roughly halves file sizes. When the card is full the camera overwrites the oldest unlocked clips, so a bigger card simply means a longer history. Check the camera's maximum supported size first — it is on every product page here.

• Format the card in the camera (not on a computer) when you first fit it. The camera chooses the file system — FAT32 or exFAT — it expects.
• Re-format monthly after backing up locked clips; it clears fragmentation that causes 'SD card error' warnings.
• If a camera beeps, shows a card error or stops recording, try a format in the camera, then a different high-endurance card. A failing card is the most common cause.
• Buy from the brand store or an authorised seller — counterfeit high-capacity cards are common online.