Printers, catalogue designers and packaging suppliers often ask for images at 300 DPI. But DPI is one of the most misunderstood settings in imaging. This guide explains what it actually means, how to work out the print size of any image, and how to convert an image to 300 DPI for free.
What DPI actually means
DPI (dots per inch) — or PPI (pixels per inch) for digital files — describes how many pixels are printed in each inch of paper. On screen it changes nothing: a 3000-pixel-wide image looks the same at 72 or 300 DPI. It only matters when the image is printed.
The simple maths: pixels ÷ DPI = inches
Print size in inches is the pixel dimension divided by the DPI. For example, an image 3000 × 4000 pixels printed at 300 DPI comes out at 10 × 13.3 inches. The same file at 150 DPI would print at 20 × 26.7 inches, but with half the sharpness per inch.
- 300 DPI: the usual standard for prints viewed up close — catalogues, lookbooks, swing tags, brochures.
- 150–200 DPI: often acceptable for posters viewed from a distance.
- 72–96 DPI: screen use only; not suitable for quality print.
Changing the DPI number vs resampling
There are two ways to 'convert to 300 DPI'. You can change only the DPI number stored in the file: the pixels stay the same, so the printed size shrinks. Or you can resample: the pixel count changes so the image prints at the same physical size at the new DPI.
Resampling up can't invent real detail that the original never had — it fills in pixels smoothly. For the sharpest print, start from the largest original you have. If your images are AI-generated, render them at 4K before converting.
How to convert an image to 300 DPI, free
The free DPI Converter resamples the pixels so the printed size stays the same:
- 1Upload a JPEG, PNG or WebP image.
- 2Choose the target DPI (72, 96, 150, 200, 300, 600, 1200) and the file format.
- 3Convert and download the print-ready file.
Print checklist for fashion brands
Before sending files to a printer:
- Confirm the final print size and work out the pixels you need (inches × 300).
- Use the highest-resolution original available; avoid screenshots.
- Ask the printer whether they need RGB or CMYK and which file format.
- Order a test print to check colour, especially for fabric colours customers will compare.
