Screen Ratio Calculator — Aspect Ratio, PPI & Diagonal
Enter your screen resolution (width × height in pixels) to get the simplified aspect ratio, diagonal in pixels, and megapixel count. Add the physical screen size in inches to also get the pixel density (PPI), pixel pitch, and physical dimensions.
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Simplified ratio: 16:9
- 1
Greatest common divisor
120Largest integer that divides both W and H evenly (Euclidean algorithm). - 2
Simplified ratio
1,920 ÷ 120 : 1,080 ÷ 120 = 16:9 - 3
Aspect ratio
16 ÷ 9 = 1.7778
How does this calculator work?
Aspect ratio = W/GCD(W,H) : H/GCD(W,H). Diagonal pixels = √(W²+H²). PPI = diagonal (px) / screen size (in); pixel pitch = 25.4/PPI mm. For 1920×1080 on a 27-inch screen: ratio 16:9, diagonal 2202 px, PPI ≈ 81.6, pixel pitch ≈ 0.31 mm.
Formula
How this is calculated
The aspect ratio is the simplest integer ratio between the width and height of a display. It is found by dividing both dimensions by their greatest common divisor (GCD). For example, 1920 × 1080 has GCD = 120, giving 16:9 — the standard widescreen ratio. Some resolutions simplify to unusual ratios (e.g. 2560 × 1080 → 64:27, known as ultra-wide 21:9).
The diagonal resolution in pixels is √(W² + H²) by the Pythagorean theorem — it is the distance across the screen in pixels. Dividing by one million gives the megapixel count, useful when comparing cameras or high-resolution displays.
If you provide the physical diagonal screen size in inches, the calculator divides the pixel diagonal by the physical diagonal to get PPI (pixels per inch), the standard measure of pixel density. Higher PPI means sharper images at a given viewing distance — roughly 90–100 PPI is typical for desktop monitors viewed at arm's length, while phones typically exceed 300 PPI. Pixel pitch is the reciprocal of PPI expressed in millimetres (25.4 / PPI).
Frequently asked questions
16:9 is the standard widescreen ratio used by most modern monitors, televisions, and smartphones in landscape mode. Common resolutions include 1280×720 (720p), 1920×1080 (1080p / Full HD), 2560×1440 (1440p / QHD), and 3840×2160 (4K / UHD).
For typical desk use at 50–70 cm, 90–110 PPI is comfortable and commonly found on 24–27 inch 1080p or 1440p displays. Above ~150 PPI (e.g. 4K on a 27 inch panel) individual pixels become invisible at normal distances. Retina displays on laptops and phones typically exceed 220–300 PPI.
2560 × 1440 does simplify to 16:9 — GCD(2560, 1440) = 160, giving 16:9 exactly. However, some resolutions such as 1366×768 (GCD = 2, ratio 683:384) only approximately match 16:9. The calculator gives the mathematically exact simplified form, which may differ from the marketed ratio.
Also known as
TG we-Calculate Editorial Team. (2026). Screen Ratio Calculator — Aspect Ratio, PPI & Diagonal [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/screen-ratio-calculator
TG we-Calculate Editorial Team. "Screen Ratio Calculator — Aspect Ratio, PPI & Diagonal." TG we-Calculate. 2026. https://we-calculate.com/calculator/screen-ratio-calculator.
TG we-Calculate Editorial Team, "Screen Ratio Calculator — Aspect Ratio, PPI & Diagonal," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/screen-ratio-calculator
@misc{wecalculate_screen_ratio_calculator, title = {Screen Ratio Calculator — Aspect Ratio, PPI & Diagonal}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/screen-ratio-calculator}}, year = {2026}, note = {TG we-Calculate} }
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