PI and File Size calculator/formulas

Formula/File size calculation for 24 bit RGB/3 bytes per pixel:
(width in inches x dpi) x (height in inches x dpi) x 3 = million bytes
For a 6x4 inch RGB image at 200 dpi example:
(6 inches x 200) x (4 inches x 200) x 3 = 2.88 million bytes

Formula/File size calculation for 32 bit CMYK/4 bytes per pixel:
(width in inches x dpi) x (height in inches x dpi) x 4 = million bytes
For a 6x4 inch CMYK image at 200 dpi example:
(6 inches x 200) x (4 inches x 200) x 4 = 3.84 million bytes

Quick Reference/Helpful Hints:

Image Type Bytes per pixel 1 bit Line art 1/8 byte per pixel 1 bit per pixel 8 bits per byte 8 bit Greyscale 1 byte per pixel 16 bit Greyscale 2 bytes per pixel 24 bit RGB 3 bytes per pixel 32 bit CMYK 4 bytes per pixel 48 bit RGB 6 bytes per pixel

Want to know how big a print you can make before you start to loose sharpness compared to film?
Here’s a formula for general cases:
Long print dimension in inches = 4 x (square root of megapixels)

Proportion calculator
To Calculate the % of Enlargement or Reduction
New Width ÷ Original Width = % and New Height ÷ Original Height = %
NOTE: If you don't get the same results from both calculations, your original is
NOT proportional to the final output dimensions

Enlargement Example:
Dimensions of Original: 8 x 10
Final Output Dimensions: 16 x 20
(16 ÷ 8) x 100 = 200%
(20 ÷ 10) x 100 = 200%

Reduction Example:
Dimensions of Original: 16 x 20
Final Output Dimensions: 8 x 10
(8 ÷ 16) x 100 = 50%
(10 ÷ 20) x 100 = 50%

RGB Conversion from 255 to 100% values
(RGB Value x 100) ÷ 255 = %

Inches to Centimeters and Inches to Millimeters Conversion
2.54 x inches = centimeters
(2.54 ÷ 100) x inches = millimeters
Quick Reference Table

Upload Calculator
mb ÷ speed = Time in sec.

Quick Reference Table:
T1 = 1.54mb per sec
Modem 56k = 56kb per sec
DSL 256k = 256kb per sec
DSL 512k = 56kb per sec
DSL 1024k = 1024kb per sec
1024kb = 1mb per sec