How to use the Screen Resolution & PPI Calculator
- Pick a preset or type your screen’s numbers. Enter the resolution in pixels and the diagonal in inches or centimeters. The diagonal is on the spec sheet or the box; the resolution is in your display settings.
- Set a viewing distance. Measure from your eyes to the screen with a tape — around 20–28 in for a desk monitor, 12–16 in for a tablet in your hands.
- Read the results. The big number is pixels per inch. Below it you get dot pitch (the width of one pixel in millimeters), the simplified aspect ratio, megapixels, the physical size of the picture area and the distance beyond which a person with 20/20 vision can no longer pick out single pixels.
- Compare two screens. Leave Compare two screens ticked to put, say, your desk monitor next to your iPad. The summary underneath shows how much denser one is, how wide the same image appears on each, and which one looks sharper from where you sit. ⇄ Swap A and B flips them.
- Copy or share. Copy results puts a plain-text summary on your clipboard; the Share link stores both screens in the address.
Why pixel density changes how your art looks
Pixel density is how tightly a screen packs its pixels, and it quietly changes every judgment you make at 100% zoom. A 27-inch 4K monitor has 163.18 pixels per inch; a 12.9-inch iPad Pro has 264.68. A 1000 px wide sketch is 6.13 in across on the monitor and only 3.78 in on the iPad. Same file, same zoom level — the iPad version looks about 38% narrower and noticeably crisper, because every pixel is 1.62 times smaller.
That is why line weights feel different when you move between devices. A 3 px inking brush that reads as a confident line on a 92 PPI office monitor turns into a hairline on a tablet. It also explains why a painting can look finished on the iPad and suddenly show rough edges and banding on a big monitor: the lower-density screen magnifies every pixel.
Density also governs whether you see pixels at all. Your eye has a resolution limit, so past a certain distance individual pixels melt into smooth tone. Know that distance and you know whether a sharper screen would actually show you more detail at your desk, or whether you’d simply be paying for pixels you cannot see.
Physical size matters too. Many monitors sold as “24-inch” have a 23.8 in viewable diagonal; at 1920 × 1080 that is 92.56 PPI instead of 91.79. The difference is small, but if you calibrate brush sizes or print previews to the screen, use the real number.
The 1-arcminute rule, worked through
Normal 20/20 vision separates details about one arcminute apart — 1/60 of a degree, or 0.000290888 radians. A pixel turns invisible once it covers a smaller angle than that.
On a 27-inch 4K monitor a pixel is 1 ÷ 163.18 = 0.00613 in wide. From a distance d, it covers an angle whose tangent is 0.00613 ÷ d. Setting that equal to tan(1′) and solving gives:
d = 1 ÷ (PPI × 0.000290888) = 3437.75 ÷ PPI
For the 4K monitor that is 3437.75 ÷ 163.18 = 21.07 in (53.5 cm). Sit at 24 in and the pixels are already below your resolution limit. For the iPad Pro the same formula gives 12.99 in, which is why it looks perfectly smooth at arm’s length but not when you lean in to check an edge. Apple’s 2010 “Retina” pitch for the 326 PPI iPhone 4 assumed a phone held 10–12 in away, and the formula agrees: 3437.75 ÷ 326 = 10.55 in.
The rule is a floor, not a guarantee. Many people, especially younger ones, see better than 20/20, and sharp high-contrast edges such as black linework on white can show stair-stepping a little beyond the computed distance.
Common screens, measured
| Screen | PPI | Dot pitch | Pixels blend beyond |
|---|---|---|---|
| 23.8″ 1920 × 1080 | 92.56 | 0.274 mm | 37.14 in (94.3 cm) |
| 27″ 2560 × 1440 | 108.79 | 0.233 mm | 31.60 in (80.3 cm) |
| 15.6″ 1920 × 1080 (laptop or pen display) | 141.21 | 0.180 mm | 24.34 in (61.8 cm) |
| 27″ 3840 × 2160 | 163.18 | 0.156 mm | 21.07 in (53.5 cm) |
| 27″ 5120 × 2880 | 217.57 | 0.117 mm | 15.80 in (40.1 cm) |
| iPad Pro 12.9″ 2732 × 2048 | 264.68 | 0.096 mm | 12.99 in (33.0 cm) |
| 65″ 3840 × 2160 TV | 67.78 | 0.375 mm | 50.72 in (128.8 cm) |
Spec sheets usually drop the decimals: Apple lists the 12.9-inch iPad Pro at 264 PPI. When two screens are close, the extra precision tells you which one is actually denser.
Tips from practice
Preview print size by zooming to the right percentage. Divide your monitor’s PPI by the print resolution: on a 27″ 1440p screen, 108.79 ÷ 300 = 36%. At that zoom, a 300 DPI file appears at roughly its printed size. To plan the pixels a print needs in the first place, use the DPI & Print Size Calculator.
Set brush sizes per device, not per habit. A brush in pixels is 1.62 times narrower in real terms on a 264 PPI tablet than on a 163 PPI monitor. If you work across both, save separate brush presets, or think in percentages of the canvas — the Procreate Brush Size Converter helps with that.
Use operating-system scaling instead of fighting tiny UI. At 150% scaling, a 27″ 4K monitor gives you the workspace of a 2560 × 1440 screen with sharper text and smoother brush cursors. Scaling only enlarges menus and text; your files keep every pixel.
Check your art at the viewing distance of its audience. A gallery print is seen from a meter away; a phone wallpaper from 30 cm. Squinting at 400% on a big monitor tells you about pixels, not about how the piece reads.