Screen Size Calculator for Physical Dimensions and PPI
The screen size calculator turns a diagonal size and resolution into a display's real physical width, height, and pixel density (PPI). Enter a value like 27 inches and 3840 × 2160, and you instantly see how wide and tall the panel actually is, plus how sharp it will look.
Manufacturers advertise only the diagonal, so a "27-inch" 16:9 monitor and a 27-inch 21:9 ultrawide have very different real dimensions. This tool fills that gap for monitor shoppers, designers, gamers, and anyone planning a desk setup, with device presets and side-by-side comparison built in.
How to Calculate Screen Size and PPI
Enter the diagonal size
Type the diagonal in inches or drag the slider. The slider snaps to common sizes from phones and tablets up to large TVs, with 27" as the starting point.
Set the resolution
Pick a preset like Full HD, QHD/2K, 4K UHD, 5K, or 8K, or type any custom width × height in pixels. Use the swap button to flip width and height for portrait orientation.
Read the results instantly
Physical width, height, area, PPI with a quality rating, aspect ratio, dot pitch, total pixels, optimal viewing distance, and display class all update as you type.
Compare or copy
Add screens to the compare panel to see sizes drawn to scale, or use Copy to put every calculated value on your clipboard for sharing or notes.
Features
Physical Dimension Calculation
Derives exact width, height, and viewable area from the diagonal and aspect ratio, shown in both inches and centimeters.
PPI Calculator with Quality Rating
Calculates pixel density automatically and grades it as Low, Standard, High, or Retina so you know how sharp the display is.
Comprehensive Device Presets
Choose from 70+ real devices across five categories: monitors, laptops, tablets, phones, and TVs, to auto-fill specs in one click.
Side-by-Side Comparison
Add up to three screens and see them drawn to scale, with resolution, physical size, PPI, and total pixel count for each.
Additional Metrics
Reads out aspect ratio, dot pitch in millimeters, total pixels in megapixels, optimal viewing distance, and display class.
Visual Preview
A live, to-scale preview shows the screen's proportions with labeled width and height while keeping the correct aspect ratio.
Detect My Screen
One click fills in your current display's resolution; the diagonal is estimated, so adjust it for a precise result.
Inches and Centimeters
Toggle every dimension between inches and centimeters, and your unit choice is remembered for next time.
Frequently Asked Questions
How do I calculate screen size from diagonal and resolution?
Enter the diagonal in inches and the resolution in pixels. The calculator uses the Pythagorean theorem on the pixel width and height to find the diagonal in pixels, then scales that to your physical diagonal to give the real width and height. Everything updates instantly as you change a value.
How do I get screen width and height from a diagonal size?
The diagonal alone is not enough, you also need the aspect ratio, which comes from the resolution. This tool splits the diagonal into width and height according to that ratio, so a 27" 16:9 panel returns roughly 23.5" wide by 13.2" tall, shown in inches or centimeters.
What is PPI and how is it calculated?
PPI (pixels per inch) is the diagonal in pixels divided by the diagonal in inches, and it measures how densely packed the pixels are. Higher PPI means sharper text and images. The calculator rates the result as Low (under 100), Standard (100–150), High (150–220), or Retina (220 and above).
What is a good PPI for a monitor or phone?
For desktop monitors viewed at arm's length, 100–150 PPI is comfortable; a 27" 1440p panel sits near 109 PPI and a 27" 4K panel near 163 PPI, both crisp. Devices held closer, like phones, benefit from 300+ PPI so text stays sharp at reading distance.
Why does the same resolution look different on different screen sizes?
Resolution is the total pixel count, not how big each pixel is. Spread 1920 × 1080 across a 24" screen and the pixels are dense (higher PPI); spread the same count across a 32" screen and they are larger and more spread out (lower PPI), so it can look less sharp.
What is dot pitch and how does it relate to PPI?
Dot pitch is the distance between the centers of adjacent pixels, measured in millimeters. It is the inverse of pixel density: a smaller dot pitch means higher PPI and a sharper image. The calculator shows both so you can read whichever spec a product lists.
How accurate is the Detect My Screen feature?
Detect reads your display's actual pixel resolution, which is accurate. The diagonal size, however, is estimated from common configurations because browsers cannot measure physical size. For an exact result, enter the diagonal from your monitor's specifications after detecting.
What is the difference between 16:9 and 21:9 aspect ratios?
16:9 is the standard widescreen shape used by most monitors and TVs. 21:9 is ultrawide, giving more horizontal room for multiple windows or immersive games. The calculator detects the ratio automatically from your resolution, so you can compare how each one changes the real width and height.
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