DPI (Dots Per Inch) and PPI (Pixels Per Inch) are exchanged at a ratio of 1:1.
Download our example image using This Link
Using Photoshop
Open your image and navigate to Image > Image Size.
Set to Pixels/Inch (PPI) under the section labelled Resolution.
Calculations are made automatically to present the resolution in any desired format.
Using GNU Image Manipulation Program
Open the image and navigate to Image > Scale Image.
Set units to Pixels/in under the section labelled X and Y resolution.
Using Grey Matter
The formula for calculating the pixel dimensions required for a 300 DPI artboard is as follows:
Multiply the width of your desired print size by the DPI value required (300).
Multiply the height of your desired print size by the DPI value required (300).
For example; the required print size is 8 inch wide x 10 inch high.
8(in) x 300(DPI) = 2400(px)
10(in) x 300(DPI) = 3000(px)
Our minimum required artboard size for a 300DPI image at 8 x 12 inch, is 2400 x 3000 pixels.
If you already know the image dimension of your image in Pixels; take the two numbers of the image dimensions and divide them by your desired print size.
For example, 1200px by 600px:
1200(px) / 2(in)
600(px) / 1(in)
= 600(PPI)
With a DPI of 600, we can easily double the print size to 4in x 2in and still remain within the 300 DPI recommended minimum.
To check the maximum size an image can be resized to; simply divide your artwork Pixel dimensions by 300 to get the maximum size in inches:
1200(px) / 300(DPI) = 4(in)
600(px) / 300(DPI) = 2(in)
4 x 2 inch
The dimensions in our example are 1463px x 1893px or 4.88in wide x 6.31in high.
1463(px) / 300(DPI) = 4.88(in)
1893(px) / 300(DPI) = 6.31(in)
The DPI is 300.
If we make the image any bigger; it will lose definition in relation to its scale.