# Calculator for scan resolution

I have a drawing that I need to scan, than to print that scan in size twice as big than original.

For example: my drawing is 20x15 cm, I need to reprint it in 40x30 cm.
How big scan resolution should be for this to work? Is this possible to calculate simply?

• What resolution do you want to print at - 150dpi, 300dpi, 600dpi, ..., 4800dpi? This drives the rest of the calculation
– mas
Jul 15 '09 at 20:10
• I know about dpi and quality print resolution, it should be 300dpi for that size of print. I just want to know the dimensions in pixels (and how to calculate them) for 20x15cm, and than for reprint too - which should be twice as big than the first one. Jul 15 '09 at 20:26
• Aside from knowing that 1 inch = 2.54 cm, what do you need? 40x30 cm == 16x12 inches == 4800x3600 pixels. Or, you're doubling linear dimensions, so scan at 600dpi to print at 300dpi. Jul 16 '09 at 1:06

The image gets scaled when it's printed. You can tell it to print any image the size you want, but if the resolution is low it will look very bad.

What determines the size of the print is the resolution (dots per inch) of the printer. It is possible to work it out from that, but it may be easier just to run a test.

Photoshop may contain some specific help on this.

With scaling disabled, or set to 1:1 -- If your scanner dpi matches your printer dpi, then it would scale 1:1. Scanning at twice the resolution would result in an image twice the size.

Since you state the printer is 300 dpi, then scanning at 600 dpi will give you a 2x image, but only if the print software doesn't do any scaling.

Minimum-quality print resolution is usually `300 DPI` (Dots Per Inch). If you want to magnify the image 2x, I would recommend scanning at least `600 DPI`.

Here is a helpful explanation.