21:9 Aspect Ratio Calculator
Get the 21:9 size for ultrawide monitors and cinematic video. Enter a width or height and the other side is filled in.
Aspect ratio
:
calculatedpx
calculatedpx
21:9
3,440 × 1,474px
px
px
Enter the size you have — the ratio is reduced to its simplest form.
64:27
What is the 21:9 aspect ratio?
21:9 is the marketing name for ultrawide screens, about 2.33 times wider than tall. Real ultrawide resolutions are not exactly 21:9: 2560 × 1080 reduces to 64:27 (2.37:1) and 3440 × 1440 to 43:18 (2.39:1). They are close to the 2.39:1 “scope” format used for cinema releases.
height = width × 9 ÷ 21
width = height × 21 ÷ 9
width = height × 21 ÷ 9
Standard ultrawide sizes
- 2560 × 1080 — UW-FHD
- 3440 × 1440 — UW-QHD
- 5120 × 2160 — 5K2K
To find the exact ratio of a monitor or video, switch to “Find a ratio” and enter its resolution.
Frequently asked questions
Is 3440 × 1440 really 21:9?
Not exactly — it reduces to 43:18 (about 2.39:1), but it is sold as 21:9.
What is 21:9 in decimal?
21 ÷ 9 = 2.333…
What height is 21:9 at 1920 px wide?
1920 × 9 ÷ 21 = 822.86 px, rounded to 823 px.