When shopping for new electronics, two of the abbreviations you’re likely to see are DPI and PPI. While they’re similar and often used interchangeably, the two are different in practice. Knowing what they both mean, as well as their importance, will help you make purchases. So, DPI vs PPI: what’s the difference? Read on to find out.
DPI: dots per inch
DPI stands for “dots per inch,” or how many individual color or black dots are physically printed. A printer may have a resolution of “300 DPI” which means in one inch there are 300 individual dots of ink. Everything else being equal, a higher DPI image of 600 will appear more detailed than a 300 DPI image, but there’s a lot more to it than that.
DPI vs DLP
You can’t judge a printer’s quality solely on its DPI claims. Other factors, essentially the “quality” of the dots themselves, will also have an effect on the printed result. In broad strokes, however, DPI specs are a good shorthand. If one printer is rated at 300 DLP and another at 3000, chances are the one with higher DLP will be able to produce far more detailed prints.
DPI vs PPI
DPI doesn’t directly relate to the resolution of digital images, nor digital devices like phones and TVs. You may hear someone say their new laptop has a screen with 600 DPI. Technically, they’re referring to PPI.
PPI: pixels per inch
PPI means “pixels per inch,” or how many pixels there are in one inch of a display, image sensor, or scanner. Pixels, a portmanteau of “picture elements,” are the tiny dots that create the image on your TV, phone, tablet, computer monitor. A typical TV has millions of pixels. The higher the resolution, the higher the PPI, due to greater pixel density (for the same size display).
If, conversely, you keep the resolution the same but increase the image size, the PPI actually goes down as there are the same number of pixels spread over a larger area. For example, a 65-inch TV with 3840 x 2160 resolution has a lower PPI than a 50-inch TV with 3840 x 2160 resolution because the pixels are larger on the 65-inch.
Don’t be fooled by PPI
Manufacturers of mobile phones, computer screens, and laptops often talk about PPI as an easier number to understand than the actual resolution of the display. But PPI is also a way to obfuscate similar specs.
Let’s say Company A’s laptop has a 13.1-inch screen and 1920 x 1080 resolution. Company B’s laptop has a 13-inch screen and 1920 x 1080 resolution, Company B can say their laptop has a higher PPI. That would technically be true (smaller screen + same resolution = higher PPI). Although, functionally, the two displays would appear to have the same amount of detail and a similar image quality.
A scanner with a higher PPI will be able to digitize documents with greater image detail compared to a scanner with lower PPI.
How much DPI or PPI do I need?
The only reason to consider DPI and PPI is to get a rough estimation of image-detail capability. We measure printed images and text with DPI, and digital displays with PPI. In neither case is this the whole story. Other factors, like the technology of the inkjet printer, laser printer, or display, can play a far greater role than the specific resolution.
Use the highest DPI
If you want a high-quality print, you should aim to use your printer’s highest DPI settings. To do this, you’ll likely need a high-resolution digital file (i.e. lots of pixels). You can’t “create” detail, so just increasing a digital photo’s resolution using software like Adobe Photoshop won’t change the quality of the output. If you’re using a professional print shop, they’ll work with you to determine what print size your specific photo can produce.
Size and resolution matter
With PPI, pay attention to the other specs for reference. What’s the actual resolution and size of the display, beyond “300 PPI” or whatever is claimed? With scanners, you can always reduce the PPI for faster scans, but you can’t increase it.
