Wondering why the read/write speeds are occasionally not shown when you’re shopping for SD or microSD cards?

We do provide this information when it’s available from the manufacturer. Just look down below at the Details section for each product on our website.

Occasionally you will only see a read speed and not a write speed. This is because the manufacturer did not provide a write speed in their product specifications for the model in question. For example, SanDisk only shows write speeds on their Extreme, Industrial and High Endurance lines, where the products are engineered for sustained writes. For their consumer grade products, like the Ultra product lineup, SanDisk only talks about “transfer speeds up to” a certain level. Their consumer lines performance may vary based on the application, so they don’t guarantee a write speed other than the Class rating.

Good news! The Class rating can help define the write speed. For example, a Class 4 card has a guaranteed write speed of 4MB/s or faster, while a Class 10 card has a guaranteed write speed of 10MB/s or faster. So when you do not see a published write speed the Class rating should be a good indicator of minimum write speed.

If you ever have questions about the performance of a specific model, or have a performance requirement for your application, please contact us and we will make some recommendations. We’re here for you!


Photo by Tim Gouw on Unsplash