Off-The-Grid Maps (SD cards) are available by state and region. Some states are less than 1 GB. Other states, like California or Texas, can be more than 16 GB of maps. How much room these maps take up on your device depends on your mobile platform.
Android: Hardly any. All of the maps are stored on the external memory card, so you don’t have to give up precious internal device memory to store and view maps. We also leave extra space on each memory card, so you can store your own apps, photos, etc. on the SD/microSD card. You can also move Off-The-Grid Maps to a bigger SD card (Learn "How to copy Off-The-Grid Maps to another memory card").
iPhone/iPad: As much or as little as you want. You can handpick what maps you want stored on your iPhone or iPad. For instance, if you are exploring Adams County, only drop the Adams County maps onto your iPhone or iPad. Most iPhones or iPads don’t have enough internal space to store an entire state’s worth of topo maps and private lands. For example, the state of Utah is 10 gigs of maps. That’s a lot, and its unlikely you have enough space to hold all of them. That’s why we allow you to pick-and-choose the maps you need and drop them into your iTunes account then sync your device. You manage your maps similar to how you manage music and videos. (Learn "How to install Off-The-Grid Maps (SD card) on my iPhone or iPad.")