Substitute 1 cm for 1 inch to find pixels per square centimeter or PPcm 2. The number of pixels in a square inch represents the resolution or pixel density of an area of one square inch. Multiply PPI × PPI to get pixels per square inch. How to Calculate PPI 2 or Pixels per Square Inch Just substitute cm for inches to find PPcm. You can use the same PPI formula above to calculate pixels per centimeter, PPcm. If a display does not have square pixels then this calculator does not apply. The PPI will be the same whether it's a horizontal or vertical or diagonal inch because pixels are square and therefore symmetric. The number of pixels per inch or PPI tells you how many pixels are in a 1 inch line on a display screen. PPI = diagonal in pixels diagonal in inches Use the formula to calculate PPI, dividing the length of the diagonal in pixels by the length of the diagonal in inches Use the Pythagorean Theorem and the screen width and height in pixels to calculate the diagonal length in pixels:ĭiagonal = width 2 + height 2 ‾ ‾ ‾ ‾ ‾ ‾ ‾ ‾ ‾ ‾ ‾ ‾ ‾ ‾ ‾ ‾ √Ģ. Follow These Two Steps to Calculate PPI:ġ. Also calculated are dot pitch, diagonal in pixels and total number in megapixels. Pixels per inch or PPcm indicates how many pixels are in a 1 inch line or 1 cm line on a display. PPI is a measure of pixel density or resolution of a smart phone screen, tablet screen or other display device. It will calculate PPI when inches are entered and calculate both PPI and PPcm when centimeters are entered. Since big prints aren’t cheap, you’ll wisely decide on a smaller size and you’ll be more satisfied with the results.Īs you can see, all it takes to calculate print size is a little know-how and a little math.The PPI Calculator finds pixels per inch ( PPI) and pixels per centimeter (PPcm). However, if you want make a 30- x 20-inch poster out of that image, you’d have a resolution of 192 ppi (5,760 ÷ 30), which isn’t high enough to print well. That’s more than enough resolution to produce an awesome print remember, you need a minimum of 240 ppi though it really depends on the printer. For example, if an image measures 3,840 x 5,760 pixels and you want an 8- x 10-inch print, take the longest edge in pixels and divide it by the longest edge in inches of the target print size: 5,760 pixels ÷ 10 inches = 576 ppi. Next, open your Mac’s Calculator app and divide the longest edge of your image (measured in pixels) by the longest edge of your desired print size (measured in inches). The Status Bar in Photoshop (top) and Elements (bottom). The dimensions appear in the second section of the panel. In Photos, select a picture and press Command-I to open the Info panel. The first step in calculating what size print you can make is to find the image’s pixel dimensions and jot them down. Besides, if you always shoot with the same cameras at the same quality settings, you only have to calculate resolution a few times to learn what print sizes you can expect to make from those devices. And if the resolution you calculate isn’t high enough to print at, say, 8 x 10 inches, then you can make an informed decision to print at a smaller size before wasting time and money. Doing so lets you know exactly what level of quality to expect from printing at a certain size. This column is about empowering you to calculate resolution manually using the image’s pixel dimensions and the size of the print you want to make. Now, this column isn’t about whether you should or shouldn’t change resolution or even how to do it in those apps. If you don’t know what you’re doing, increasing resolution can trash an image because the app will add (interpolate) fake pixels that weren’t really captured. Other apps, such as Adobe Photoshop, Photoshop Elements, and Pixelmator also alert you to resolution deficiency in their print dialog boxes but they also let you fiddle with the resolution setting in their Image Size dialog boxes. Why? Because those apps calculate the resolution for you whenever you ask them to print an image at a certain size if you don’t have enough resolution, the app tells you so. Adobe Photoshop Lightroom doesn’t flaunt the setting either you only encounter it when exporting images. To keep things simple, Apple Photos won’t let you see image resolution, much less change it. However, if you forked out big bucks for an inkjet printer that can spray ink at higher resolutions-say, 1440 dpi or 2880 dpi-you can sometimes get a better result by aiming for a higher resolution in your calculation. Generally speaking, you need a resolution of at least 240 ppi to produce a nice print on most inkjet printers and online printing services. The lower the resolution, the bigger the pixels, which makes for blocky prints resembling a pile of Legos. Small pixels make for smooth, high-quality prints. The higher the resolution of an image, the smaller the pixels.
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