Aspect Ratio Calculator
Find the simplified aspect ratio for a width and height, or scale a dimension to match a target ratio.
1,920 × 1,080 simplifies to 16:9
An aspect ratio describes the proportional relationship between a width and a height, written as W:H (e.g. 16:9). To simplify a ratio, divide both numbers by their greatest common divisor — 1920 and 1080 share a greatest common divisor of 120, so 1920:1080 reduces to 16:9.
To go the other direction — finding a missing width or height that fits a target ratio — multiply the known dimension by the ratio of the other side. For a 16:9 ratio with a known width of 1920, the height is 1920 × (9 ÷ 16) = 1080.
Worked examples:
- 1920 × 1080 → 16:9 (1.78:1) — standard HD/widescreen video
- 800 × 600 → 4:3 (1.33:1) — standard/fullscreen
- 16:9 ratio, width 2560 → height 1440
How do I calculate an aspect ratio from pixel dimensions?
Divide both the width and height by their greatest common divisor (GCD). For example, 1920 and 1080 share a GCD of 120, so 1920:1080 simplifies to 16:9. This calculator does that automatically — enter the width and height and it shows the simplified ratio.
How do I find a missing width or height for a target ratio?
Switch to "From Ratio" mode, enter the target ratio (or pick a preset like 16:9), select which dimension you already know, and enter its value. The calculator scales the ratio to compute the other dimension — e.g. a 16:9 ratio with a known width of 1920 gives a height of 1080.
What is the difference between 16:9 and 16:10?
16:9 (1.78:1) is the standard widescreen ratio used by HD/4K video, TVs, and most laptop screens. 16:10 (1.6:1) is slightly taller and common on some monitors and tablets — the same width, but 11% more vertical space than 16:9 at the same width.
Why does my ratio not match a common preset?
Not every width/height pair reduces to a well-known ratio like 16:9 or 4:3 — custom or cropped dimensions often simplify to less common fractions (e.g. 1000×1500 reduces to 2:3). That's expected; the calculator still shows the exact simplified ratio and its decimal equivalent.
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Updated October 8, 2026