# Increasing DPI for image reduction

I have an image that is 66x50 inch and 72 dpi, which looks great on any monitor because it's huge, but I actually have to reduce the image size to print it on a 44 inch paper.

I know that for print jobs to look good the dpi has to be around 300. So, should I increase the dpi to 300 and then reduce the image size or 72 is good enough if the image has to be reduced?

• "300 dpi equals good looking" is true for books, (top) magazines and calendars - in other words, stuff people actually look closely to. It also would look good on a billboard, except that's overkill, because nobody's going to look at a billboard from 10 inches away. What is the purpose of your large-size print? Commented Oct 15, 2015 at 17:23
• Digitally stored raster images are not,cannot and never will be in inches. What you have is a 4752px x 3600px image. Only the pixels are stored and in some formats, a flag for dpi is supported which is really just a suggestion. If you print this on paper or other physical substrate only then can it be actually measured in inches. If you print the exact untouched image at 66x50 inches it will then be 72dpi. If you print the exact untouched image at 15.84 x 12 inches, then it will be 300dpi. Resampling as mentioned in the answers is another word for (making up or throwing away pixels). Commented Oct 15, 2015 at 19:12
• @ jongware: yes, I forgot to mention that the print is intended to be hanged in a wall where you can look at it from up close. Commented Oct 15, 2015 at 21:08

Your image isn't big enough to boost the dpi from 72 to 300, at least not at your required size of 44 inches.

Taking a 66x50 in image at 72 dpi, and wanting to print it at 300 dpi means the largest the image can be is 15.84x12 in

At 44 inches in width, your image would be 33.3 in in height and have a dpi of 108, which is certainly an improvement over 72 dpi but nowhere near the desired 300 dpi.

And as Jongware mentioned you need to figure what the purpose of the print will be and from how far it will be viewed from. Maybe you won't even need 300 dpi.

An easy way to figure these numbers out is to open your image in Photoshop and then going to Image > Image Size... and then unchecking the Resample checkbox. You can then adjust the dimensions and resolution and the other numbers will adjust to match.

Here's what it looks like:

The 300 ppi is recomended for comercial printing with an output of 150 lpi. So the first question is: Are you using the file for comercial printing, for example a calendar or something?

If the answer is no, then don't be scared of using diferent resolutions than 300 ppi, like printing a poster on a plotter for hanging on the wall of your home.

So 4752x3600 px is a decent image. At 44 inches will give you a 108 ppi resolution. You won't see thoose pixels at 50 cm. But you still can improve that resolution a bit.

In my opinion you should only resample an image by an exact multipyer. In this case 200% using Bicubic sharper (In Photoshop)

This will give you a very good resolution of 216 ppi. This resolution is fine for that size.

• 300dpi also usually presumes reading at about arms length. Larger formats like posters and billboards are often less than 300. Commented Oct 15, 2015 at 19:16