# What DPI do I need for printing?

Choose a print density by the image, viewing distance and printer's instructions, then calculate the pixels needed at the final size.

> Start with 300 pixels per inch for photographs viewed up close, then follow your print shop's specification. Large posters viewed farther away may work at 150 PPI. Use 600 PPI when the workflow specifically calls for it. Image PPI describes pixel density; a printer's DPI rating describes its ink dots, a different measurement.

## Image pixels and printer dots do different jobs

PPI measures how many image pixels occupy one inch of paper. DPI measures the printer's dot placement. A printer can use many ink dots to reproduce the colour of one image pixel, so its advertised hardware DPI does not directly specify the pixel density your photo needs.

PrintScale uses the familiar DPI label for the density of the delivered image. In the table below, 300 PPI therefore corresponds to its 300 DPI output setting.

## Work back from the intended print

Take the width and height after cropping, and divide by the physical size in inches. That gives the effective PPI. If you know the desired density instead, multiply each print edge in centimetres by `PPI ÷ 2.54` to find the required pixels.

Ask the print shop about paper, viewing distance and its preferred file settings. Avoid increasing density simply because a larger number is available: additional pixels can increase file size without improving visible detail.

## Pixel reference table

| Paper | Size, cm | 150 PPI, pixels | 300 PPI, pixels | 600 PPI, pixels |
| --- | --- | --- | --- | --- |
| A4 | 21.0 × 29.7 | 1,240 × 1,754 | 2,480 × 3,508 | 4,961 × 7,016 |
| A3 | 29.7 × 42.0 | 1,754 × 2,480 | 3,508 × 4,961 | 7,016 × 9,921 |
| A2 | 42.0 × 59.4 | 2,480 × 3,508 | 4,961 × 7,016 | 9,921 × 14,031 |
| A1 | 59.4 × 84.1 | 3,508 × 4,967 | 7,016 × 9,933 | 14,031 × 19,866 |

Dimensions are calculated from the nominal paper size, rounded to a whole pixel and exclude bleed. This is a general reference table; some combinations exceed PrintScale's current output limits.

## Common questions

### Does changing 72 DPI to 300 DPI improve the photo?

Changing only the density metadata does not add pixels or recover detail. It changes the default physical print size. Resampling changes the pixel count, but the quality of those extra pixels depends on the source and the enlargement method.

### Is 600 DPI always better for photos?

No. A 600 PPI image has four times the pixel count of a 300 PPI image at the same print size. Whether that improves the print depends on the source detail and printing process. Follow the printer's specification and compare a proof when unsure.

## Further reading

[Adobe's image size, resolution and resampling guide](https://helpx.adobe.com/photoshop/desktop/crop-resize-transform/resize-adjust-resolution/image-size-resolution-and-resampling.html) explains how these settings relate. The [free calculator](/calculator) converts your actual pixel dimensions into print sizes without an account.

When you know the target, [check your image in PrintScale](/#tool).