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DPI vs PPI: Difference Between Dots Per Inch and Pixels
DPI (Dots Per Inch) measures print resolution using physical ink dots. PPI (Pixels Per Inch) measures screen resolution using digital pixels. DPI is for printers; PPI is for screens.
Overview
DPI (Dots Per Inch) measures print resolution using physical ink dots. PPI (Pixels Per Inch) measures screen resolution using digital pixels. DPI is for printers; PPI is for screens.
Quick Answer
DPI (dots per inch) is a printer metric. It measures how many tiny ink dots a printer deposits per inch. PPI (pixels per inch) is a screen and image metric. It measures how many pixels are packed into each inch of a display or digital file. Both describe density per inch, but they apply to different contexts.
Side-by-Side Comparison
| Attribute | DPI (Dots Per Inch) | PPI (Pixels Per Inch) |
|---|---|---|
| Stands for | Dots per inch | Pixels per inch |
| Applies to | Printers and printing | Screens and digital images |
| Measures | Ink dot density | Pixel density |
| Typical values | 600 - 2880 (printers) | 72 - 460 (screens) |
| Higher value means | Smoother, finer prints | Sharper, crisper display |
| Controlled by | Printer hardware/driver | Display hardware |
| Affects file size? | No (metadata only) | No (metadata only) |
When DPI Applies
DPI is relevant when you are printing. Your printer's DPI setting determines how finely it can reproduce the image data. A 1200 DPI laser printer can lay down ink dots much more precisely than a 300 DPI printer, producing smoother gradients and finer text.
When someone says "save this image at 300 DPI," they usually mean 300 PPI - they want 300 pixels per inch at the intended print size. The printer's actual DPI is a separate hardware specification.
When PPI Applies
PPI is relevant for screens and image files. Your monitor has a fixed PPI determined by its resolution and physical size. When preparing images for a specific print size, PPI tells you how many pixels you need. At 300 PPI, a 10x8-inch print requires a 3000x2400 pixel image.
Common Confusion
The confusion arises because software like Photoshop labels image resolution as "DPI" even though it is technically PPI. The image file stores pixels, not dots. The dots only exist when the image is printed. In practice, understanding that pixel dimensions are what matter - for both screen and print - resolves most confusion.
Use our DPI Calculator to determine print dimensions, or the PPI Calculator to find the pixel density of any screen.
Practical Quality Notes for DPI vs PPI
This guide is most helpful when the result is tied to a real workflow, not treated as a loose number. For DPI vs PPI, verify print size, source pixel dimensions, and the DPI value requested by the printer or export workflow. That context prevents the common mistake of copying a pixel value into a print, web, or CSS workflow where the reference size is different.
DPI vs PPI should be checked with the formula, a realistic example, and the actual output requirement before you export or publish. If the number looks unexpectedly large or small, check the unit direction first, then check the DPI, base font size, viewport width, or physical measurement that controls the calculation.
A good review pass for DPI vs PPI is simple: calculate once, compare against a known example, and preview the final output at the size people will actually see. DPI (Dots Per Inch) measures print resolution using physical ink dots. PPI (Pixels Per Inch) measures screen resolution using digital pixels. DPI is for printers; PPI is for screens.
Checks Before You Use the Result
- Confirm that DPI vs PPI is using the same input unit your source file or design brief uses.
- Save the DPI, viewport, or font-size setting next to the final DPI vs PPI value so another person can reproduce it.
- Preview the DPI vs PPI output on the target medium before sending it to print, publishing it, or adding it to CSS.
- Recalculate DPI vs PPI after resizing, cropping, changing aspect ratio, or changing the root font-size or viewport assumption.
When the Number Needs a Second Look
Recheck the result if the project moves from screen to print, from desktop to mobile, from one social platform placement to another, or from a draft export to a production file. Small context changes can make a correct DPI vs PPI answer wrong for the final job.
Sources
Reference Sources
These external references support the page's conversion formulas, resolution guidance, and unit explanations.
w3.org
W3C: CSS Values and Units Module Level 4
Specification covering absolute lengths and resolution units such as px, in, cm, mm, pt, and dpi.
Visit source
developer.mozilla.org
MDN: CSS values and units
Reference guide for CSS measurement units and how browsers interpret physical and relative sizes.
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developer.mozilla.org
MDN: <resolution>
Reference for resolution units including dpi, dppx, and dpcm used in screen and print discussions.
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developer.mozilla.org
MDN: image-resolution
Explains how raster image resolution metadata interacts with CSS and print-oriented image workflows.
Visit source
Frequently Asked Questions
In casual use, many people swap the terms. However, DPI technically applies to printers (ink dots per inch), while PPI applies to screens and digital images (pixels per inch). Using the correct term avoids ambiguity in professional settings.
When referring to an image file, '300 DPI' usually means 300 PPI - the image has 300 pixels per inch at its intended print size. The printer's actual DPI (often 720-2880) determines how finely those pixels are reproduced with ink dots.
Neither. Web browsers ignore the DPI/PPI metadata in image files. Only pixel dimensions matter for web display. A 1200x800 image renders the same on screen regardless of its DPI setting.
72 DPI was the legacy Mac screen resolution, and 96 DPI is the Windows default. These defaults have no impact on how the image appears on screen - they only affect the default print size calculation.