Pixels Per Inch
Calculate pixels per inch (PPI) from screen resolution width, height, and diagonal size. Free PPI calculator with dot pitch, megapixels, and interactive charts.
About This Calculator
The Pixels Per Inch (PPI) Calculator measures the pixel density of any display — monitor, laptop, tablet, smartphone, or TV. By entering your screen's horizontal and vertical pixel resolution along with the diagonal size in inches, you get an instant calculation of PPI, dot pitch, total pixel count, and megapixels. This tool is essential for graphic designers, photographers, video editors, and anyone comparing display sharpness across devices.
How PPI is calculated
PPI is derived from the Pythagorean theorem. First, the diagonal resolution in pixels is found: dₒ = √(w² + h²) where w and h are the horizontal and vertical pixel counts. Then PPI is the diagonal pixels divided by the diagonal screen size in inches: PPI = dₒ / dᵢ. The dot pitch is the inverse of PPI converted to millimeters (dot pitch = (1 / PPI) × 25.4). Total pixels is simply w × h, and megapixels divides that by one million.
How to use this calculator
Enter your screen resolution (e.g., 1920 horizontal pixels and 1080 vertical pixels for a Full HD display) and the diagonal screen size in inches (e.g., 27 for a typical desktop monitor). Click "Calculate PPI" to see the pixel density, diagonal pixel count, total pixels, megapixels, and dot pitch. The chart and breakdown table give you a visual comparison of the key display metrics.
Regional notes
Screen measurements are standardized globally — diagonal sizes are always given in inches by manufacturers, and pixel counts are resolution-independent. PPI values are comparable across all regions. Smartphones sold in India, the US, and the UK often share identical displays, so this calculator works universally with no region-specific adjustments needed.
Frequently Asked Questions
What is PPI and why does it matter?
PPI stands for pixels per inch and measures the pixel density of a display. A higher PPI means sharper text and more detailed images. It matters most when choosing monitors, smartphones, and laptops because it determines how crisp content appears on screen.
How do I calculate PPI?
PPI is calculated as the square root of the sum of the squares of horizontal and vertical pixels, divided by the diagonal screen size in inches. The formula is: PPI = √(w² + h²) / d, where w and h are pixel dimensions and d is the diagonal in inches.
What is a good PPI value for a monitor?
For desktop monitors, 90–110 PPI is common and adequate. For laptops, 140–200 PPI is typical. Smartphones often exceed 300 PPI. Apple's Retina display threshold is around 300 PPI for phone viewing distances and 220 PPI for laptop distances.
What is the difference between PPI and DPI?
PPI (pixels per inch) refers to digital displays and measures pixel density on screens. DPI (dots per inch) traditionally refers to printing and measures how many ink dots a printer can produce per inch. On screens they are often used interchangeably, but DPI is more relevant for print output.
How do I measure my screen diagonal?
Screen diagonal is measured from one corner to the opposite corner of the visible display area, not including the bezel. You can check your device specifications on the manufacturer's website, in system settings, or measure it yourself with a tape measure in inches.
What is dot pitch?
Dot pitch is the distance between the centers of two adjacent pixels on a display. It is calculated as the inverse of PPI. Smaller dot pitch values indicate tighter pixel spacing and sharper images. It is typically expressed in millimeters.
Does higher PPI always mean better quality?
Higher PPI generally means sharper images, but the benefit diminishes beyond a certain point due to human eye limitations. The ideal PPI depends on viewing distance — closer screens like phones benefit from higher PPI, while TVs viewed from farther away need less density.
What resolutions correspond to common PPI values?
A 27-inch 1080p display has about 81 PPI, 1440p has about 109 PPI, and 4K has about 163 PPI. A 24-inch 1080p monitor gives 92 PPI. Smartphones like the iPhone 15 Pro Max (6.7-inch, 2796x1290) deliver around 460 PPI.