PPI Calculator (Screen Pixel Density)
Pixels per inch from resolution and diagonal, with pitch, size, CSS pixels and sharpness.
Try before you buy.
- Free preview: your screen’s resolution and the first common screens of the comparison (up to 3), with the pixel density, the diagonal and every other figure hidden.
- Locked until you unlock it: copy.
- Unlock: Pro pass, ₹179 for 30 days, a one-time payment that never renews.
Ways to unlock shows how to get the full result.
Printing this result is locked in the free preview.
Screen
The size the screen is sold as: corner to corner of the picture.
The scaling the system uses: CSS pixels = pixels ÷ ratio.
Result
Compared with common screens
| Screen | PPI |
|---|
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About the PPI Calculator (Screen Pixel Density)
Pixel density, in pixels per inch (PPI), is how tightly a screen packs its pixels: the number of pixels along the diagonal divided by the diagonal’s length, PPI = √(width² + height²) ÷ diagonal. A 27-inch 2560 × 1440 monitor has 108.79 PPI; a 6.1-inch 2532 × 1170 phone has about 457. Type a resolution and the diagonal the screen is sold as, or a pixel density to find the diagonal, and the calculator works out the rest.
You get the pixel pitch (the distance between pixels), the screen’s width and height in centimetres and inches, its aspect ratio and megapixels, the CSS viewport at the device pixel ratio your system uses, the ratio that would make a CSS pixel the size of the CSS reference pixel at your viewing distance, how many pixels per degree you see from there, the distance beyond which 20/20 vision can no longer pick out single pixels, and Android’s nearest density bucket — with your screen ranked among common phones, tablets, laptops, monitors and TVs. Without a pass you see a free preview: your screen and the first common screens of the comparison, with the pixel density (or diagonal) and every other figure hidden.
How to use it
- Type the screen’s resolution in pixels, or pick a common one; This screen fills in what your browser reports.
- Type the diagonal in inches or cm (the size the screen is sold as). To work backwards, choose Find the diagonal and type the PPI instead.
- Choose the device pixel ratio your system uses (100 % scaling is 1×, 200 % is 2×) and your viewing distance.
- Read the pixel density and the figures below it, and see where the screen ranks. With a Pro pass, Copy results copies them all; in the free preview copying is locked.
Examples
2560 × 1440, 27 in
108.79 PPI · pixel pitch 0.2335 mm · 59.8 × 33.6 cm
√(2560² + 1440²) = 2937.21 pixels along the diagonal; 2937.21 ÷ 27 = 108.79.
1920 × 1080, 24 in
91.79 PPI; single pixels blend for 20/20 vision from about 95 cm (37.5 in)
1 ÷ (91.79 × tan 1′) = 37.45 in: beyond that, one pixel is smaller than one minute of arc.
2532 × 1170 on 6.1 in, 3× pixel ratio
About 457 PPI; a CSS viewport of 844 × 390 px
3840 × 2160 at 163 PPI
27.03 in (68.7 cm)
Common uses
- Comparing monitors before buying: a 27-inch 4K screen has 50 % more pixels per inch than a 27-inch QHD one.
- Checking how sharp text and images will look from where you sit.
- Working out CSS viewports and image sizes for phones, tablets and laptops at their pixel ratios.
- Choosing Android drawable densities for a screen.
The formula
The diagonal in pixels follows from Pythagoras: √(width² + height²). Divide by the diagonal in inches and you have PPI; divide 25.4 mm by the PPI and you have the pixel pitch. The width and height in inches are the diagonal × width ÷ diagonal pixels and the diagonal × height ÷ diagonal pixels. Screens are sold by their diagonal rounded to a tenth of an inch, so a maker’s own PPI figure can differ from the calculated one in the last digit.
CSS pixels and the device pixel ratio
Web pages are laid out in CSS pixels. The device pixel ratio (DPR) is how many screen pixels one CSS pixel takes: the CSS viewport is the resolution ÷ DPR (a 2532 × 1170 phone at 3× is 844 × 390 CSS px). CSS defines its reference pixel as the visual angle of one pixel on a 96 dpi screen at arm’s length, 28 inches — about 0.0213° (CSS Values and Units 4). The page shows the ratio that would make a CSS pixel exactly that size from your viewing distance: PPI × distance ÷ 2688. Systems choose their own scaling steps, so this is a reference, not what your device uses.
When pixels disappear
Normal (20/20) vision resolves detail of about one minute of arc (visual acuity). A pixel smaller than that can no longer be seen on its own, which happens beyond 1 ÷ (PPI × tan 1′) ≈ 3438 ÷ PPI inches. The same idea as pixels per degree: at about 60 pixels per degree single pixels stop being visible to 20/20 eyes. People with sharper eyes than 20/20 can still see them a little further away.
Android densities
Android groups screens into density buckets — ldpi (~120 dpi), mdpi (~160, the baseline), hdpi (~240), xhdpi (~320), xxhdpi (~480) and xxxhdpi (~640) — and sizes layouts in density-independent pixels: px = dp × (dpi ÷ 160) (Android Developers). The page names the bucket nearest your screen’s density; the device itself may report a value between buckets.
Limitations
- The diagonal is taken as the visible picture’s; rounded corners, notches and curved edges are not subtracted.
- This screen reads the resolution and pixel ratio your browser reports; with display scaling or a zoomed page this can differ from the panel’s native resolution, and no browser reports the physical size.
- The viewing figures assume 20/20 vision and a screen seen straight on.
- In the free preview you see your screen and the first common screens of the comparison; the pixel density (or diagonal), the other figures, where your screen ranks and copying unlock with a pass.
Privacy
Everything happens in your browser. What you enter or open here is not uploaded or stored by MySmartCoPilot.
Frequently asked questions
What do I get without a pass?
Without a pass, PPI Calculator (Screen Pixel Density) shows your screen’s resolution and the first common screens of the comparison (up to 3), with the pixel density, the diagonal and every other figure hidden. Until you unlock it, the result can’t be copied. A Pro, Premium or Ultimate pass, a one-time payment that never renews, unlocks the full result. The pricing page lists the passes and their prices.
How do I calculate PPI?
Square the width and the height in pixels, add them, take the square root and divide by the diagonal in inches. For 1920 × 1080 on 24 inches: √(1920² + 1080²) = 2202.9, and 2202.9 ÷ 24 = 91.79 PPI.
Is PPI the same as DPI?
For screens people often say DPI, but PPI is the correct term: a screen has pixels, while DPI counts a printer’s ink dots. Android’s “dpi” buckets mean pixels per inch too.
What is a good PPI for a monitor?
It depends on the scaling you want. At arm’s length (28 inches) a CSS pixel matches the CSS reference pixel at about 96 PPI with 100 % scaling and about 192 PPI with 200 %, so 90–110 PPI suits 1× and around 190 PPI suits 2× at the same text size. If the page says pixels blend at a distance shorter than where you sit, single pixels will not be visible to 20/20 eyes.
Can it measure my screen automatically?
It can read the resolution and pixel ratio your browser reports with This screen, but no browser reveals a screen’s physical size, so you still type the diagonal.
Why does the result differ from the maker’s PPI?
Makers round the diagonal they advertise, so the last digits can differ: a 2532 × 1170 phone sold as 6.1 inches comes out at 457 PPI, while a 460 PPI panel of that resolution measures 6.06 inches.