Screen PPI & Size Calculator
Enter a screen’s resolution and diagonal to get its pixels per inch, pixel pitch, real width and height, and the distance at which its pixels disappear. Add a viewing distance for TVs, or read your own screen’s resolution.
How to Use
- Enter the screen’s resolution (width and height in pixels), or type a name such as
1440por4Kin the width box. On a computer, Use my screen fills in the display you are looking at. - Enter the diagonal from the spec sheet, in inches or centimetres. A unit typed in the box, such as
68.6 cm, overrides the switch. - Optionally add how far away you sit, in any unit:
24 in,8 ft,2.4 m. - Read the pixel density, physical size, pixel pitch and the distance beyond which pixels blend together.
- For a computer screen, pick a Windows scaling setting to see how much desktop space you get and how large text will look.
Worked Example
A 27-inch 1440p monitor. The diagonal in pixels is √(2560² + 1440²) = √8,627,200 = 2,937.2. Divide by the 27-inch diagonal: 2,937.2 ÷ 27 = 108.79 pixels per inch. Each pixel is 25.4 ÷ 108.79 = 0.2335 mm across. The width is 27 × 2560 ÷ 2,937.2 = 23.53 in (59.8 cm) and the height 27 × 1440 ÷ 2,937.2 = 13.24 in (33.6 cm). A 20/20 eye resolves 1 arcminute, so single pixels blend together beyond 1 ÷ (108.79 × tan 1′) = 31.6 in (80 cm). At a desk distance of 24 in you are closer than that: 45.6 pixels per degree, sharp but not “retina”. The same panel at 4K is 163.18 PPI and 68.4 pixels per degree, past the 60 mark.
A 65-inch 4K TV from 8 ft. √(3840² + 2160²) = 4,405.8 pixels ÷ 65 = 67.78 PPI, and the screen is 56.65 × 31.87 in. At 96 in it shows 2 × 96 × tan 0.5° × 67.78 = 113.6 pixels per degree, nearly twice the 60 a 20/20 eye can resolve, and fills 2 × atan(56.65 ÷ 192) = 32.9° of your view, inside the 30–40° range. A 1080p screen of the same size would show 56.8 pixels per degree from there: just under the limit.
Show Work
PPI of Common Screens
Widths and heights are for 16:9 screens unless the resolution says otherwise. “Pixels vanish” is the distance beyond which 20/20 vision cannot see single pixels.
| Screen | Resolution | PPI | Pixel pitch | Width × height | Pixels vanish beyond |
|---|---|---|---|---|---|
| 21.5-inch monitor | 1920 × 1080 | 102.5 | 0.248 mm | 18.7 × 10.5 in | 34 in |
| 24-inch monitor | 1920 × 1080 | 91.8 | 0.277 mm | 20.9 × 11.8 in | 3.1 ft |
| 24-inch 16:10 monitor | 1920 × 1200 | 94.3 | 0.269 mm | 20.4 × 12.7 in | 3.0 ft |
| 27-inch monitor | 1920 × 1080 | 81.6 | 0.311 mm | 23.5 × 13.2 in | 3.5 ft |
| 27-inch monitor | 2560 × 1440 | 108.8 | 0.233 mm | 23.5 × 13.2 in | 32 in |
| 27-inch monitor | 3840 × 2160 | 163.2 | 0.156 mm | 23.5 × 13.2 in | 21 in |
| 27-inch 5K monitor | 5120 × 2880 | 217.6 | 0.117 mm | 23.5 × 13.2 in | 16 in |
| 32-inch monitor | 3840 × 2160 | 137.7 | 0.184 mm | 27.9 × 15.7 in | 25 in |
| 34-inch ultrawide | 3440 × 1440 | 109.7 | 0.232 mm | 31.4 × 13.1 in | 31 in |
| 49-inch super ultrawide | 5120 × 1440 | 108.5 | 0.234 mm | 47.2 × 13.3 in | 32 in |
| 13.3-inch laptop | 2560 × 1600 | 227.0 | 0.112 mm | 11.3 × 7.0 in | 15 in |
| 14-inch laptop | 2560 × 1600 | 215.6 | 0.118 mm | 11.9 × 7.4 in | 16 in |
| 15.6-inch laptop | 1920 × 1080 | 141.2 | 0.180 mm | 13.6 × 7.6 in | 24 in |
| 43-inch TV | 3840 × 2160 | 102.5 | 0.248 mm | 37.5 × 21.1 in | 34 in |
| 55-inch TV | 3840 × 2160 | 80.1 | 0.317 mm | 47.9 × 27.0 in | 3.6 ft |
| 65-inch TV | 3840 × 2160 | 67.8 | 0.375 mm | 56.7 × 31.9 in | 4.2 ft |
| 75-inch TV | 3840 × 2160 | 58.7 | 0.432 mm | 65.4 × 36.8 in | 4.9 ft |
| 85-inch TV | 3840 × 2160 | 51.8 | 0.490 mm | 74.1 × 41.7 in | 5.5 ft |
Formulas
From 72 PPI to Retina
The first Macintosh in 1984 had a 9-inch screen of 512 × 342 pixels, about 72 per inch. That matched the printer’s point, 1/72 of an inch, so a 12-point letter on screen was the same size on paper. Windows chose 96 pixels per “logical inch” instead, slightly larger text for screens viewed from farther away, and that 96 is still the baseline: Windows scaling of 100% is 96 DPI, 125% is 120, 150% is 144 and 200% is 192.
For decades desktop monitors stayed close to those numbers, which is why most software assumed them. When phones and laptops reached two and three times the density, operating systems began drawing everything at 2× or 3× so text stayed the same physical size and simply became sharper. Apple named this “Retina” with the iPhone 4 in 2010: 326 pixels per inch, chosen so that at 10–12 inches a pixel is about 1 arcminute wide.
That arcminute comes from eye testing. Herman Snellen’s 1862 chart is built on letters whose strokes are 1 arcminute wide at the “normal” line, the line now called 20/20. It is a guide rather than a hard limit: many people, especially young ones, see better than 20/20, and fine edges and aliasing can be noticed beyond it. For TVs and cinemas the other question is how much of your view the screen should fill; SMPTE’s guideline for cinema design (EG 18-1994) asks for the screen to fill at least 30° of the view, and THX recommends about 36–40°.
About This Calculator
This calculator turns a resolution and a diagonal into what you can actually see: pixel density, pixel pitch, physical width and height, aspect ratio, and the distance beyond which single pixels blend together. With a viewing distance it adds pixels per degree and the angle the screen fills, and for TVs the screen size or seat that gives a 30° or 40° view. For computers it shows what each Windows scaling setting does to desktop space and text size.
Use my screen reads the resolution your browser reports for the display it is on, multiplied by its scaling factor; set the browser zoom to 100% first. Browsers do not report physical size, so the diagonal must come from the spec sheet. Everything runs in your browser and nothing is sent anywhere.
Related tools: Aspect Ratio Calculator, Dead & Stuck Pixel Test and the Video & Display Connector Chart.
Frequently Asked Questions
What is a good PPI for a monitor?
At normal desk distance, about 90–110 PPI gives classic-size text with no scaling: a 24-inch 1080p screen is 91.8 PPI and a 27-inch 1440p screen is 108.8. Higher densities look sharper but need scaling: a 27-inch 4K screen is 163.2 PPI, so at 100% text is only 0.59 times the classic size, and around 150–175% looks normal.
Is 4K worth it on a TV?
It depends on size and distance. On a 65-inch screen, 20/20 vision stops seeing 4K’s pixels beyond about 4.2 ft and 1080p’s beyond about 8.4 ft. From a couch at 8 ft, 1080p is already close to the limit, so the extra sharpness of 4K is small; it matters more on bigger screens or closer seats. Better HDR and colour are separate from resolution.
Why doesn’t my result match the spec sheet?
Advertised diagonals are rounded: a “27-inch” monitor may have a 26.9-inch viewable area, and phone makers measure the screen as a full rectangle even though the corners are rounded. A small difference in the diagonal moves the PPI by the same percentage; use the exact viewable size from the data sheet if you have it.
What is the difference between PPI and DPI?
PPI counts the pixels per inch on a screen. DPI is strictly for printers, which build each pixel out of many ink dots. People often say DPI for screens anyway, and Windows calls its scaling setting DPI: 100% scaling is 96 DPI, 125% is 120, 150% is 144 and 200% is 192.
How far should I sit from my TV?
A common rule is to make the screen fill 30–40° of your view: 30° is the minimum in SMPTE’s cinema guideline, and THX recommends about 36–40°. For a 65-inch 16:9 screen that is about 8.8 ft for 30° and 6.5 ft for 40°. Enter your distance and the calculator shows the angle and the screen size that would fill 30° or 40°.
How do I use the Screen PPI & Size Calculator?
Simply type your numbers and read the result, which refreshes the instant you change something. There is nothing to submit and nothing to wait for.
Do I need to install or sign up for anything?
Not at all — it runs in the browser with nothing to install and no account. After it loads once, it even works without an internet connection.
Is my information private?
Yes. Everything happens in your browser. Nothing you type is sent to a server or saved anywhere.
Common Use Cases
Choosing a monitor
27-inch 1440p is 108.8 PPI and works at 100%; 27-inch 4K is 163.2 PPI and needs about 150–175% scaling, which leaves the desktop space of 2560 × 1440 at 150%.
Picking a TV size
A 65-inch TV at 8 ft fills 32.9° of your view, inside the 30–40° range; a 55-inch at 9 ft fills only 25°.
Laptop scaling
A 15.6-inch 1080p laptop is 141 PPI: at 100% text is 0.68 times the classic size, while 150% brings it back to 1.02.
Real-world size for designs
Pixel pitch tells you how big a 44-pixel button really is: 44 × 0.2335 mm = 10.3 mm on a 27-inch 1440p screen.
Phones and tablets
A 6.1-inch 2556 × 1179 phone is about 461 PPI; at 12 inches its pixels are far below what the eye can resolve.
Last updated: