With all of the different memory cards, standards and versions available it’s sometimes difficult to select the card that will best meet your requirements.
MicroSD (and “full” SD) cards are put into classes using standards as defined by the SD Association however the standards only define the minimum speeds. Manufacturers generally market based on the sequential read speed.
These are the standards and the minimum write speeds
Since most dash cameras record at at least 1080p a Class 10 or UHS-1 (U1) card is normally the minimum recommended. UHS-3 (U3) cards are more expensive and would be overkill for current dashcams.
Below we have benchmarked a few cards we have used for testing purposes using CrystalDiskMark 5.0.2, starting with the most expensive to the cheapest.
Note that for dashcams the most important figure below is Seq(uential) Write (3rd figure down on the right). Typically anything above 3MB/s will work perfectly fine for 1296p video.
SanDisk Extreme 64GB UHS-3 MicroSD (~R800)
Samsung Evo 32GB UHS-1 MicroSD (~R250)
Strontium Nitro 433X 16GB UHS-1 MicroSD (~R150)
Kingston 16GB Class 10 MicroSD (~R100)
SanDisk Ultra 8GB Class 10 SD (<R100)
ALL of these cards meet the minimum requirements of 10MB/s write speed for Class 10 or UHS-1.
ALL of the cards exceed the minimum write speed requirement for current dashcams of around 3MB/s (which would result 10GB per hour of video).
Given that the read speeds of the Strontium Nitro 433X are exceptionally high we would recommend it for dashcam usage, although any Class 10 or UHS-1 cards would be suitable.
When it comes to selecting capacity, keep in mind that 32GB normally holds around 3-5 hours worth of video. Dashcams will “loop” and record over the oldest files when the card is full so you will essentially always have the last “x” number of hours available. Generally a 32gb card will store enough video for anyone driving to work and back each day and give you a chance to copy any video off it if anything happens. If you are travelling more or perhaps would like to record a full days worth of driving (eg. for fleet vehicles) then a larger card would be recommended.