Why is the Actual Capacity of Memory Cards Less Than the Indicated Capacity?

Have you ever bought a memory card marked as 128GB, but when inserted into the device, the displayed capacity is less than 128GB? This is not a quality problem of the memory card, but because the calculation method of memory card capacity is different. This article will explain why the actual available capacity is less than the indicated capacity.

1. Different Capacity Calculation Methods Memory card manufacturers use the decimal (Decimal) calculation method, while electronic devices (such as computers, mobile phones, etc.) use the binary (Binary) calculation method.

Decimal calculation: 1GB = 1,000MB (manufacturer's indication) Binary calculation: 1GB = 1,024MB (device actual display) Therefore, when a 128GB memory card marked by the manufacturer is inserted into the device, the device will calculate it in binary, and the actual capacity displayed will be about 117GB.

2. System Files and Reserved Space Some devices will automatically reserve space for system files or applications, resulting in a further reduction in the displayed available capacity. For example, Android phones may pre-install system files, occupying a certain amount of storage space, so the available capacity will be less than the theoretical capacity.

3. File System Occupies Space Memory cards usually need to be formatted before use, and different file systems (such as FAT32, exFAT) will also occupy a certain amount of storage space during the formatting process. This is also one of the reasons why the actual capacity is smaller than the indicated capacity.

4. How to Avoid Buying Inferior Cards? Some inferior or counterfeit memory cards may indicate false capacity, and the actual capacity is far less than the indicated value. To avoid being deceived, it is recommended to purchase brand memory cards and use specialized software such as H2testw to test the actual capacity and speed of the memory card.