What Are The Different Types of Memory Card Speeds?

Like if this guide is helpful
What Are The Different Types of Memory Card Speeds?

Nearly every portable electronic device currently available incorporates a memory card to maximise performance and storage. A memory card supplements the relatively small amount of memory which is available on the hard drive of gadgets, enabling the device to hold more information and undertake increasingly sophisticated activities. Memory card speed has a significant impact on the ability of equipment to work well, with various aspects of photography being particularly affected by speed considerations. Being aware of the different types of speed measurement and which speeds are most appropriate for facilitating the intended activities is crucial when deciding the memory card that will make the most suitable purchase.

Different Measurements of Memory Card Speeds

Perusal of the technical information relating to speed which accompanies a memory card can appear confusing, as there are several different measurements which are used to gauge it. Speed class (which is dependent on the write speed of a card) and rated speed are the two main speed assessments which are undertaken on a memory card in order to compare it with other cards. In addition, each card has a read speed which can vary even between cards of the same speed class. Note that there can be variations in read speed and rated speed between different manufacturers, even if the card's Speed Class is the same. While it can be tempting to opt for a card which stipulates it offers a higher rated speed, this does not necessarily result in increased equipment performance, which may well be determined by Speed Class. The parameters of speed within a particular Speed Class can also vary between manufacturers, although the differences are often quite small and will not make a noticeable difference to operational efficiency. Factors such as price, length of guarantee and versatility are often better determinants of the memory card which offers superior value for money, rather than consideration of speed differentials in isolation. Detailed in the table given below are the main differences between speed class, rated speed and read speed, as well as brief information on the general uses which are pertinent to each speed type.




Speed Class

The speed class is arrived at by measuring the minimum sustainable speed over time. While speed may peak to a level towards the top range of the speed class, it will not drop below the designated speed class level. This results in a card which produces a steady stream of data at a reasonably constant speed. Constant speed is particularly important for devices such as camcorders. The Speed Class is dependent on the write speed of the card. This is the measurement of how quickly a card can save information from a device when it is in use. The higher the measurement, the swifter the transfer of data from the device to the card will be. Uses

The Speed Class is usually a more useful indicator of suitability for the majority of electronic devices. Most gadgets function best when having access to a steady speed from a card. This is particularly the case for camcorders and video cameras, where images are required to be saved at a constant rate for a protracted period of time. Relying on the rated speed alone might mean that periodically frames would not be saved when the rated speed dipped, resulting in a choppy film when it is replayed.

Rated Speed

The rated speed is normally defined as the average speed at which the memory card operates in normal conditions. Although the speed of the card may drop below the rated speed periodically, most of the time the card will perform at the rated speed. The rated speed is of particular interest to users of devices where a large amount of data needs to be saved in a very short period of time, such as when taking high resolution still shots with a camera.

A high rated speed is normally of less importance for devices where a steady data stream is required for optimum performance. Camcorders, video cameras, phones, or a laptop generally don't need to be able to save data extremely fast over short periods of time, which is the major advantage of a high rated speed. The key popular use of a high rated speed memory card is in an advanced digital camera which is used for still photography. Having a high rated speed reduces the time needed to save the large amounts of data which are intrinsic to a high resolution still picture before the next one can be taken. If in doubt about the rated speed required for any device, check the manufacturer's handbook for further information.

Read Speed

This speed relates to the velocity of data transfer between devices, rather than how fast data may be saved. It determines the speed of image retrieval, or how fast downloading might take from the internet or elsewhere.

Read speed is of greater importance in devices where data retrieval is a key consideration. A slow read speed means tardier functioning. In addition to having a Speed Class assigned, older memory cards may also carry an x designation. This relates to a previous method of categorisation and is generally recognised to relate to read speed rather than write speed.

Speed Class Categories

In order that consumers can more easily pick the memory card which will best suit the intended device, cards have now been divided into five categories, or Speed Classes. The following table gives details of each Class, as well as brief details of which devices most commonly utilise each type. It should be remembered that in addition to Speed Class, cards also come in various sizes and categories, such as High Capacity or Extended Capacity. It is important to choose a card which is compatible with the chosen device in all respects, not just Speed Class. When purchasing a memory card, note that the Class Speed will be written on the front of the card, enabling easy recognition.

Class Categories


Class 2 (minimum write speed of 2MB/second)

While it is always best to use the Speed Class recommended by the manufacturer of the equipment, Class 2 cards are generally suggested for use during standard-definition video recording. Class 2 is not fast enough to effectively deliver High Definition (HD) video. It is normally used in a standard camera for taking average quality still photographs.

Class 4 (minimum write speed of 4MB/second)

Generally a Class 4 card can support HD video recording and is able to cope with the demands most amateur photographers will make on it.

Class 6 (minimum write speed of 6 MB/second)

Faster than Class 4, the Class 6 can capture images at a more rapid rate than Class 4. There is a tendency for Class 6 and 4 to be used interchangeably

Class 10 (minimum write speed of 10 MB/second)

This is often the category recommended for HD still shot consecutive photography and HD video recording over a protracted period of time.

UHS Cards. These are further subdivided into Class I and Class II, capable of operating at speeds of 50 and 104 MB/second respectively.

Offering ultra-fast write speed, there are currently only a few devices on the market which are designed to utilise them. These are normally extremely sophisticated cameras which are designed with professional use in mind.

Buying Memory Card of a Specific Speed on eBay

eBay offers a good selection of memory cards suitable for the majority of electronic devices currently available. When commencing a search for memory cards, the best method is to click on the All Categories tab, then select the Electronics & Technology section. From there, click through to Mobile Phones & Communication followed by Mobile Phones & Accessories. Finally, select the Memory Cards category to find a range of suitable products. It is also possible to search by memory card manufacturer or by Speed Class, for example Class 6 Memory Card. In all cases, when purchasing a memory card consult the manufacturer's recommendations for the equipment to ensure compatibility.


The invention of Speed Class categories has resulted in a useful standardisation process for memory cards. It enables consumers to be clear regarding which card is going to best meet the technical requirements of the gadget and to purchase a card which offers the best value for the price, irrespective of the card manufacturer. By purchasing a memory card which is tailored to meet the required specification of the piece of equipment, purchasers can be confident of experiencing optimum functionality and performance from their product.

Have something to share, create your own guide... Write a guide
Explore more guides