How to Use Screen Size Calculator
The Screen Size Calculator helps you understand the exact physical dimensions and pixel density of any display in seconds.
- Enter Diagonal — type the screen diagonal in inches (e.g., 27 for a 27-inch monitor).
- Select Aspect Ratio — choose 16:9, 16:10, 4:3, 21:9, or enter a custom ratio. The Screen Size Calculator uses this to derive physical width and height.
- Select Resolution — pick a preset (1080p, 1440p, 4K, 5K) or enter a custom resolution to calculate PPI and dot pitch.
- Choose Output Unit — switch between inches, centimeters, and millimeters to see dimensions in your preferred unit.
The result panel shows width, height, area, PPI, dot pitch, and the numeric aspect ratio simultaneously.
Formula & Theory — Screen Size Calculator
The Screen Size Calculator uses the Pythagorean theorem to derive physical screen dimensions from the diagonal.
Physical width and height:
Width = Diagonal × Aspect_W / sqrt(Aspect_W² + Aspect_H²)
Height = Diagonal × Aspect_H / sqrt(Aspect_W² + Aspect_H²)
PPI (Pixels Per Inch):
PPI = sqrt(Horizontal_px² + Vertical_px²) / Diagonal_inches
Dot Pitch:
Dot Pitch (mm) = 25.4 / PPI
| Symbol | Meaning |
|---|---|
| Diagonal | Screen diagonal in inches |
| Aspect_W, Aspect_H | Aspect ratio numerator and denominator |
| Horizontal_px, Vertical_px | Horizontal and vertical pixel counts |
Area Calculation
Area is simply Width × Height in the chosen unit. The Screen Size Calculator converts inches to cm or mm before computing area, so units remain consistent.
Use Cases for Screen Size Calculator
The Screen Size Calculator is useful across a wide range of display-related decisions:
- Monitor buying — compare a 24-inch 1080p monitor against a 27-inch 1440p model to understand the actual size and sharpness difference before purchasing.
- Multi-monitor setup — use the Screen Size Calculator to ensure monitors in a multi-display setup are physically compatible in height.
- Mobile and tablet design — designers entering device diagonal sizes to check physical UI element sizes on phones, tablets, and phablets.
- TV vs. monitor comparison — see whether a 32-inch TV used as a PC monitor will have an acceptable PPI for close viewing distances.
- Laptop screen evaluation — compare 13-inch vs. 15-inch laptops at different resolutions to choose between portability and clarity.
- Digital signage — calculate the pixel density of large-format displays for wayfinding or advertising installations.
Whether you are choosing a display for gaming, design work, video editing, or office productivity, the Screen Size Calculator delivers all the critical metrics you need in one place.