What is the maximum size sd card (Gigabites)?

Speed class choices.
about compatibility with host devices before choosing your card, it is important that you understand how to use your memory card to it greatest ability. sdxc memory cards and devices (digital cameras, video cameras, laptops, etc.) are now available. learn how to use your new sdxc memory card to optimize its performance.
confirm compatibility before inserting your sdxc memory card, confirm the device is compatible with the sdxc standard by locating an sdxc logo on the device or referring to the device's user manual or manufacturer information.

understanding backwards compatibility

• sdxc memory cards must only be used with sdxc devices.
• sdxc devices can use sd memory cards, sdhc memory cards and sdxc memory cards.
• sdhc memory cards can be used with sdhc devices and sdxc devices.
• sdhc devices can use both sd memory cards and sdhc memory cards.
• sd devices can only use sd memory cards.

You can get major information about SD cards capacity on https://www.sdcard.org/consumers/choices/index.html .

SD cards max out at 2GB. SDHC cards range from 4GB to 32GB. SDXC cards go 64GB on up.

Your camera manual will tell you which type(s) your camera is compatible with. If you require further assistance, please add a comment to this question and specify the make and model of your camera.