Screen Size, Resolution & PPI Calculator
Calculate screen width and height from diagonal size and aspect ratio, find pixel density (PPI), and compare actual viewing area across monitors and TVs.
Screen Size Calculator — interactive calculator, computed instantly in your browser.
Screen Dimensions Explained: Diagonal, Aspect Ratio, and PPI
From Diagonal to Width & Height
Key Takeaway: The diagonal only sets scale — aspect ratio splits it into width and height, while resolution determines pixel density (PPI).
Marketing labels every panel by its diagonal, but that number alone won't tell you whether a monitor fits your desk or a TV fits your wall. Real dimensions come from splitting the diagonal with the aspect ratio, and perceived sharpness comes from dividing pixel counts by that diagonal — the pixel density, or PPI.
1. Diagonal to Width and Height
- For 16:9, √(16² + 9²) = 18.358 — a 27″ panel is 23.5″ wide × 13.2″ tall
- A 32″ 16:9 TV is ~28.1″ × 15.8″ — nearly 200 sq in of glass versus 161 sq in for 27″
- Ultrawide 21:9 at the same diagonal is much shorter: a 34″ ultrawide is only ~13″ tall but 31.4″ wide
- Height is why a 32″ TV feels bigger than a 27″ monitor even though both are "16:9"
2. Pixel Density (PPI) and Sharpness
A 27″ QHD panel works out to ≈109 PPI, the same 109 PPI you get from a 24″ 1080p screen — identical sharpness at different sizes. 4K on 27″ jumps to ≈163 PPI, where the OS needs scaling to keep text readable. Pixel pitch follows directly: 25.4 mm ÷ PPI, so 109 PPI = 0.233 mm between pixel centers. Sitting closer than about one metre makes individual pixels visible on a 109 PPI screen.
3. Choosing by Use Case
- Office / coding: 24–27″ at 109–163 PPI; 1440p on 27″ sweet-spots sharpness without heavy scaling
- Photo & video work: ≥160 PPI with an ultrawide 21:9 or 16:10 ratio for timeline and toolbar space
- TV viewing: multiply seating distance by 0.55 for 1080p, 0.40 for 4K — a 55″ 4K TV is comfortable at ~2.0 m (6.5 ft)
- Gaming: resolution ÷ refresh — check your GPU can drive the pixel budget before prioritizing size
🔗 Display & Bandwidth Cross-References
Bigger diagonal does not always mean more visible area — a 27" 16:9 monitor and a 34" ultrawide show different widths at similar heights. Explore our 🌐 Tech & Network Hub for more hardware utilities.
Once the panel is picked, budget its bandwidth with the data usage tools below.
Frequently Asked Questions (Screen Size Calculator)
Split the diagonal using the aspect ratio: width = diagonal × W ÷ √(W² + H²), height = diagonal × H ÷ √(W² + H²). For 16:9 divide by 18.358 — a 27″ screen gives 23.5″ × 13.2″.
PPI (pixels per inch) is diagonal pixels divided by diagonal inches. ~109 PPI (24″ 1080p) is standard, ~140–163 PPI (27″ 1440p/4K) looks crisp, and Apple-class Retina displays sit above 220 PPI where individual pixels stop resolving at normal viewing distance.
No — what matters is pixels per degree of vision. A 32″ 1080p screen (69 PPI) looks blurrier than a 24″ 1080p (92 PPI), and oversized panels need more desk depth. Match resolution to size so PPI stays above ~95 for monitor use.
The GPU is sending a signal with a different ratio than the panel's native one — this causes stretching or black bars. Set the output to the panel's native resolution (e.g. 2560×1440 on a 16:9 QHD monitor) for a pixel-perfect match.
A common rule: seating distance ≈ 0.4 × diagonal for 4K (55″ ≈ 1.9–2.0 m / 6.5 ft) and 0.55 × diagonal for 1080p. Beyond ~1.5 m you can no longer distinguish 4K from 1080p at typical TV sizes.