DPI / PPI Calculator

Calculate dots per inch and pixels per inch from screen or print dimensions for optimal image resolution.

How to Use DPI / PPI Calculator

1

Enter dimensions

Type the width and height in pixels of your image.
2

Set physical size

Enter the desired print size in inches or centimeters.
3

View DPI/PPI

See the resulting dots per inch for your print settings.

Tested tool guide Tested browser tools Checked August 16, 2026

What DPI / PPI Calculator does, with a checked example

Pixel dimensions alone do not reveal how densely an image will appear at a particular size. This calculator divides a horizontal or vertical count of pixels or dots by the corresponding physical length in inches. For screens and raster images, the result is pixels per inch, or PPI. For a defined dot grid, it is dots per inch, or DPI. The common mistake is treating image PPI as a printer's hardware DPI, even though a printer may use several ink dots to reproduce one image pixel.

Worked example

A concrete input and expected output from the current implementation.

Input

Pixel size: 1200 x 600 px
Physical size: 6 x 3 in

Expected output

200 PPI

The horizontal density is 1200 / 6 = 200 PPI, and the vertical density is 600 / 3 = 200 PPI. Because both axes agree, the placement has a single density of 200 PPI.

How the result is produced

Per-axis density

Given a raster width of W pixels and a physical width of I inches, density is W / I PPI. The same division applies vertically. If both axes produce the same value, the pixel and physical rectangles have matching aspect ratios. If they differ, the proposed placement requires cropping, padding, or nonuniform scaling before one PPI value can describe it.

Dots versus pixels

For print dots, DPI counts defined dots across one inch. For a raster image or display panel, PPI counts pixels across one inch. Both are count-per-length measurements, so their arithmetic can look identical. A calculated image PPI does not establish a printer's native DPI or determine how many printer dots will be used to reproduce each pixel.

Good uses

Checking the density of a 4000 x 3000 pixel photograph placed in a 10 x 7.5 inch print.
Comparing the physical pixel density of 2560 x 1440 monitors with different screen sizes.
Testing whether the pixel dimensions left after cropping meet a print provider's requested PPI at the final output size.

Limits and checks

A density calculated from image pixels is PPI, even when software or print instructions loosely call it DPI.
The pixel aspect ratio must match the intended physical aspect ratio if one density value is expected for both axes.
Operating-system scaling changes the size of interface elements in logical pixels, but it does not change a panel's physical pixel density.

Common questions

Can I convert an image's PPI directly to printer DPI?

No, not in general. An image prepared at 300 PPI does not imply that the printer operates at 300 DPI. Printer dots describe the output device or screening process, and multiple dots may contribute to one image pixel. Use the calculator for geometric density, then consult the printer or print provider for its required image PPI and device settings.

Does a higher PPI always make the result look sharper?

No. At a fixed physical size, additional source pixels increase PPI, but visible sharpness also depends on source detail, resampling, the display or printing process, and viewing distance. Changing only an image's PPI metadata does not create new pixels or detail. The calculator reports the size-density relationship, not perceived image quality.

References and verification

The example and behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.