What really changes
Take a 2400 by 3000 pixel image. At 72 DPI it would print 33.3 by 41.7 inches. At 300 DPI it prints 8 by 10 inches. The pixels are identical. Only the printed size is different.
Divide the pixel count by 4.17 (300 divided by 72) to see the new size. A 1000 pixel wide image is 13.9 inches wide at 72 DPI and 3.3 inches wide at 300 DPI.
Why not just resize in an editor?
In an image editor, you can tick "resample" when you change the DPI. Then the program invents new pixels and the picture changes. Without resample, the result is the same as this tool, but you need to open a large program. Here, nothing is resampled.
If you really need a bigger print
You need more pixels. Go back to the original design and export at a larger size, or start from a higher resolution photo. Upscaling programs can add pixels, but they guess the new detail.
Questions
- Is 72 DPI bad?
- It is fine for screens. It is a problem for print only because print programs use the value to decide the size. The picture itself is not worse.
- Will my 72 DPI image look sharper at 300 DPI?
- No. Sharpness depends on the pixels. This tool does not change them.
- What is the new size of my image?
- Add the file. The row shows the print size in inches and centimeters at 300 DPI.