Bit depth capacity for raster dataset cells

The bit depth (pixel depth) of a cell determines the range of values that a particular raster file can store, which is based on the formula 2ⁿ (where n is the bit depth). For example, an 8-bit raster can have 256 unique values that range from 0 to 255.

The following table shows the range of values stored for different bit depths:

Bit depth	Range of values that each cell can contain
1 bit	0 to 1
2 bit	0 to 3
4 bit	0 to 15
Unsigned 8 bit	0 to 255
Signed 8 bit	-128 to 127
Unsigned 16 bit	0 to 65535
Signed 16 bit	-32768 to 32767
Unsigned 32 bit	0 to 4294967295
Signed 32 bit	-2147483648 to 2147483647
Floating-point 32 bit	-3.402823466e+38 to 3.402823466e+38

Range of values by pixel depth

The complex bit depth is supported for reading and displaying purposes. This bit depth exists in a number of raster formats, including radar formats such as Radarsat, and .gff.

Dive-in:

There are exceptions to this that are hidden. A grid dataset is always stored as 32 bit (either signed, unsigned, or floating point), but ArcGIS shows it above as being the most appropriate bit depth with regard to the cell values it contains.

Legacy:

ArcInfo Workstation always displays the bit depth of the grid.

Esri's products contain all the designations of unknown values within their raster datasets. The unknown values are NoData. Internally, a real value must be used to store the NoData cells. Accordingly, when NoData is added to a raster that already has a full bit range (meaning that there is at least one cell in the raster extent occupying all the values in the bit range, for example, when 0 to 255 are all represented), it is promoted to the next higher bit depth. For example, a hillshade grid with cell values of 0 to 255, which then has NoData added to it, is represented as unsigned 16 bit.