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

Unsigned 64 bit

0 to 18446744073709551616

Range of values by pixel depth

An additional type of bit depth, called complex, 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.


There are exceptions when the true bit depth does not match the bit depth property within the Raster Properties window. While Esri Grid rasters are always stored with a 32 bit depth (either as signed or unsigned integer, or floating point), ArcGIS will display the bit depth property with the most appropriate bit depth according to the range of cell values the raster contains..

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.

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