Calculating Image Sizes

To calculate the size of an image:

File Size (bits) = Width x Height x Channels x Bits per channel 

Example 1

For example for a normal 2000 by 3000 color RGB image:

• Width: 2000
• Height: 3000
• Channels: Red, Green, Blue
• Bits per channel: 8 ( 0 to 255)

2000 x 3000 x 3 x 8 =  144,000,000 bits

Convert to Bytes:

144,000,000 / 8 = 18 Megabytes

Example 2

For example for a 2000 by 3000 color Grayscale image:

• Width: 2000
• Height: 3000
• Channels: Grey
• Bits per channel: 8 ( 0 to 255)

2000 x 3000 x 1 x 8 =  48,000,000 bits

Convert to Bytes:

48,000,000 / 8 = 6 Megabytes

Example 3

For example for a custom 40 by 30 Black and White Image

• Width: 40
• Height: 30
• Channels: 1 (Black)
• Bits per channel: 1

40 x 30 x 1 x 1 = 120 Bits

Convert to Bytes:

120 / 8 = 15 Bytes

Example 4

For example for a custom 50 x 20 8 bit image

• Width: 40
• Height: 30
• Channels: 1
• Bits per channel: 8 bits per pixel.

50 x 20 x 8 = 8000 bits

8000 / 8 = 1000 bytes

1 Kilobyte