SD Cards: Types, Sizes and Speed

Written by Brent Topa | Jul 18, 2012 1:48:00 PM

When shopping for a new memory card, most consumers would say, “I need more space.” There are a lot of factors involved in selecting one of these portable storage devices. So what should you look for when purchasing a new memory card? Here’s a quick guide to help:

What Type of Card Does Your Device Use?

Every device is different, but there are three kinds of cards that are most popular: secure digital (SD), micro secure digital (microSD), and compact flash (CF).

SD Cards:
SD Cards are the most common for point-and-shoot cameras. They are removable which helps eliminate the need for a USB cable to transfer images. Many times the camera can accept card sizes up to 32GB and up to Class 6 speed. If the camera can also take video (or HD video), a Class 10 card (or UHS-I card) may be required.
MicroSD Cards:
MicroSD cards can be found in smaller devices, such as cell phones. The form factor was originally designed because SD cards were too large for phones. Just like cameras, most phones can accept sizes up to 32GB. In order to insert a microSD card into a machine to read the files, an SD card adapter is required. These come packaged with the memory card.
CF Cards:
CF cards are the most durable card type, which means professional photographers rely on them for high-end DSLR and video cameras. CF cards extend to sizes of 256GB and 1000X speeds. This allows them to record real-time HD video and capture high-resolution photos.

What Size Card Do I Need?

So, you’ve figured out what type of card you need. Next, you need to determine what storage size. Depending on your usage (and budget), you can make sure you get the card that best fits your needs. SanDisk has created a chart based on file size to show approximately how much data your card will hold:

Megapixels	File Size	1GB	2GB	4GB	8GB	16GB	32GB	64GB	128GB
4MP	1.2 MB	715	1,430	2,861	5,722	11,444	22,888	45,776	91,552
5MP	1.5 MB	572	1,144	2,288	4,577	9,155	18,310	36,620	73,240
6MP	1.8 MB	476	953	1,907	3,814	7,629	15,258	30,516	61,032
7MP	2.1 MB	408	817	1,634	3,269	6,539	13,078	26,156	52,312
8MP	2.4 MB	357	715	1,430	2,861	5,722	11,444	22,888	45,776
10MP	3.0 MB	286	572	1,144	2,288	4,577	9,155	18,310	36,620
12MP	3.6 MB	238	476	953	1,907	3,814	7,629	15,258	30,516
14MP	4.2 MB	204	408	817	1,634	3,269	6,539	13,078	26,156
16MP	4.8 MB	178	357	715	1,430	2,861	5,722	11,444	22,888
22MP	6.6 MB	130	260	520	1,040	2,080	4,161	8,322	16,644

Movie, Normal Photo & Music Storage

The SD Card Association has created this chart for movie, normal photo and music storage:

	2 GB	4 GB	8 GB	16 GB	32 GB
Movies: (Hi-def movie recording MPEG-4. H.264)
Fine mode (13Mbps/CBR)	20 min	40 min.	80 min.	160 min.	320 min.
Normal mode (9Mbps/VBR)	30 min.	60 min.	120 min.	240 min.	480 min.
Economy mode (6Mbps/VBR)	45 min.	60 min.	180 min.	360 min.	720 min.
Photos:
10 Megapixels, 3648x2736, Fine mode	770 photos	1,540 photos	3,080 photos	6,160 photos	12,320 photos
Music:
ACC, MP3 HQ mode, 128Kbps	34 hr. 7 min.	68 hr. 14 min.	136 hr. 27 min.	272 hr. 54 min.	545 hr. 48 min.

* All numbers are approximate. Actual storage will depend on size of data and compression used.

What speed do I need?

Now we know what type and what size card you need. The last part can be tricky because it needs to be compatible with the specifications that your device can accept.

In reference to SD and microSD cards, most devices are compatible with speeds up to Class 6. This is true for basic point-and-shoot cameras, cell phones, etc. Newer equipment can accept Class 10, as well as UHS-1 depending on the application. UHS-1 is typically for HD video recording and real-time broadcasts.

CF cards are rated by “X” speeds, which translates to their transfer rate in megabytes per seconds. Again, refer to your device’s manual for the recommended speeds. Just remember – the faster the speed, the higher the price.

You’re all set…except for the brand.

SanDisk is arguably the most popular brand in the world, but other companies such as Transcend, Kingston, and Lexar give them a run for their money. The big companies are great for regular cards, but there are third-party companies that specialize in the high-end cards such as UHS-1 SD and high-speed CF cards. Once you have figured out the specs of your new card, check out online reviews to find the brand you’re most comfortable with.

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