Digital Image Resolution Converter
Convert image resolution between dots per inch, pixels per inch and metric units.
Written by Rahman · Last reviewed
Quick answer
Image resolution converts between dots or pixels per unit length. One dot per inch is 39.37 dots per metre, and dpi and ppi convert one to one. They describe printing and display respectively but are numerically identical. Print work is typically 300 dpi, while screens have historically run 72 to 96 ppi.
| Dot per metre (dot/m) | 1 |
| Dot per centimetre (dot/cm) | 0.01 |
| Dot per inch (dpi) | 0.0254 |
| Pixel per inch (ppi) | 0.0254 |
About the Digital Image Resolution Converter
Digital image resolution describes how densely pixels or dots are packed, expressed as pixels per inch (PPI) or dots per inch (DPI). Higher values mean sharper images.
This converter is used in printing, photography and screen design.
An image has pixels; DPI only appears when it is printed
A digital image is a grid of pixels and nothing more. It has no physical size until it is printed or displayed, and the DPI or PPI value stored in its metadata does not change how much detail it contains, only how large it will be laid out.
The relationship is one division. A 1200 by 1800 pixel image printed at 300 DPI covers 4 by 6 inches. The same file printed at 72 DPI covers about 16.7 by 25 inches, spreading the identical pixels over a much larger area and looking correspondingly coarser. Changing the DPI figure alone resizes the print; it neither adds nor removes information.
- Resampling is the operation that genuinely changes pixel count, and enlarging that way invents detail rather than recovering it.
- To find the pixels needed for a print, multiply the intended size in inches by the target DPI.
- 300 DPI is the usual target for photographic printing; large formats viewed from a distance are routinely produced at far less.
DPI and PPI are not interchangeable
The two terms are used as synonyms constantly and describe different things. PPI (pixels per inch) describes the image or the display: how many pixels occupy an inch of screen or print area. DPI (dots per inch) describes a printer: how many ink dots it can place in an inch.
They differ because most printers cannot produce a full-colour pixel with a single dot. Several ink dots combine to reproduce one pixel's colour, so a printer quoting a high DPI is not offering that many pixels of detail. This is why printer specifications and image resolutions cannot be compared directly.
- Screen density is properly PPI, though device specifications often print DPI.
- High-density displays render multiple physical pixels per CSS pixel, which is why web images are frequently supplied at two or three times their layout size.
- For screen work, pixel dimensions are the only figure that matters: the DPI value stored in the file is ignored entirely by browsers.
Frequently Asked Questions
What is the difference between DPI and PPI?
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PPI (pixels per inch) describes screen images, while DPI (dots per inch) describes printed output. The values convert directly here.
What resolution is good for printing?
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Photo-quality printing typically uses 300 DPI, while screen images are usually 72 to 96 PPI.
Does higher resolution always look better?
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Only up to a point. Beyond what the eye can see at normal viewing distance, extra resolution adds file size without visible benefit.