How it works
To resize, the missing side is width × height ratio ÷ width ratio, or the reverse. 1280 pixels wide at 16:9 is 1280 × 9 ÷ 16 = 720 pixels high.
To find a ratio, both sides are divided by their greatest common divisor: 2560 × 1440 ÷ 160 = 16:9. Decimal sides are scaled up first, and the nearest well-known ratio is named when it is within 1.5%.
Common aspect ratios
| Ratio | Typical use | Example size |
|---|---|---|
| 16:9 | Widescreen TV, YouTube, monitors | 1920 × 1080 |
| 9:16 | Vertical video: Shorts, Reels, TikTok | 1080 × 1920 |
| 4:3 | Classic TV, iPad, slides | 1024 × 768 |
| 3:4 | Portrait tablet | 768 × 1024 |
| 21:9 | Ultrawide monitor, cinema (nominal) | 2560 × 1080 |
| 32:9 | Super ultrawide monitor | 5120 × 1440 |
| 16:10 | Laptops, MacBook | 1920 × 1200 |
| 3:2 | 35 mm photos, DSLR | 6000 × 4000 |
| 2:3 | Portrait photo prints | 4000 × 6000 |
| 1:1 | Square posts, profile images | 1080 × 1080 |
| 4:5 | Portrait feed posts | 1080 × 1350 |
| 5:4 | Older monitors, 8×10 prints | 1280 × 1024 |
| 2.39:1 | Cinema scope | 4096 × 1716 |
| 1.85:1 | Cinema flat | 3996 × 2160 |
Tips
- Ultrawide monitors sold as 21:9 are really 64:27 (2560 × 1080) or close to it (3440 × 1440 is 43:18).
- HD, Full HD, 4K UHD and 8K TV formats are all 16:9, as defined by ITU-R BT.709 and BT.2020.
- For photos, crop to the target ratio before resizing so nothing gets stretched.
Standards and sources
- ITU-R BT.709: HDTV picture format (16:9) · ITU
- ITU-R BT.2020: UHDTV 4K and 8K picture formats (16:9) · ITU
- ITU-R BT.601: standard-definition TV, 4:3 and 16:9 · ITU
Last reviewed October 17, 2026
Frequently asked questions
How do I calculate the height for 16:9?
Multiply the width by 9 and divide by 16. For 1920 pixels wide that is 1080; for 1280 it is 720.
What ratio is 2560 × 1440?
16:9. Both numbers divide by 160, giving 16 and 9. It is the same shape as 1920 × 1080, just with more pixels.
Is 21:9 exactly 21 to 9?
Not usually. It is a marketing name: 2560 × 1080 monitors are 64:27 (2.37:1) and 3440 × 1440 is 43:18 (2.39:1). Cinema scope is about 2.39:1.
Why should video sizes be even?
Common video formats store colour at half resolution, which needs even widths and heights. Odd sizes can fail to encode or get a black line added.