Aspect Ratio Calculator
Find a missing width or height, turn any resolution into its ratio, or resize without stretching. Results update as you type.
How the calculator works
An aspect ratio is the width of a frame compared with its height. The calculator uses three formulas:
- Height from width: height = width × ratio height ÷ ratio width. For 16:9 at 1280 px wide: 1280 × 9 ÷ 16 = 720.
- Width from height: width = height × ratio width ÷ ratio height. For 4:5 at 1350 px tall: 1350 × 4 ÷ 5 = 1080.
- Ratio from a resolution: divide the width and the height by their greatest common divisor. 1920 and 1080 share a divisor of 120, so 1920 × 1080 is 16:9.
Pixels are whole numbers, so when a result has decimals, round it. A 16:9 frame 1000 px wide works out to 1000 × 9 ÷ 16 = 562.5 px tall, so you would use 562 or 563; if your software asks for even numbers, use 562 or 564.
What aspect ratio is 1080x1920?
1080 × 1920 is a 9:16 aspect ratio. The greatest common divisor of 1080 and 1920 is 120; 1080 ÷ 120 = 9 and 1920 ÷ 120 = 16. It is the upright version of 1920 × 1080, the Full HD frame defined as 16:9 in ITU-R BT.709, turned on its side. Vertical formats use this shape: Meta's Instagram Reels ad specs list a 9:16 ratio. For upload sizes on each platform, see our social media image sizes guide.
Common aspect ratios and example sizes
| Ratio | Decimal | Example size (px) | Notes |
|---|---|---|---|
| 1:1 | 1.00:1 | 1080 × 1080 | Square |
| 4:5 | 0.80:1 | 1080 × 1350 | Portrait |
| 9:16 | 0.56:1 | 1080 × 1920 | Vertical (upright 16:9) |
| 2:3 | 0.67:1 | 4000 × 6000 | Portrait 3:2 |
| 3:2 | 1.50:1 | 6000 × 4000 | Same shape as a 36 × 24 mm film frame |
| 4:3 | 1.33:1 | 1024 × 768 | Upright form is 3:4 |
| 16:10 | 1.60:1 | 1920 × 1200 | Sold as WUXGA on 16:10 monitors |
| 16:9 | 1.78:1 | 1920 × 1080 | Full HD, 4K UHD (BT.709, BT.2020) |
| 64:27 | 2.37:1 | 2560 × 1080 | Sold as "21:9" ultrawide |
| 43:18 | 2.39:1 | 3440 × 1440 | Sold as "21:9" ultrawide |
The Full HD and 4K sizes come from the international broadcast standards BT.709 and BT.2020, both 16:9. The ultrawide rows match monitors that LG sells as 21:9, such as the 29WQ600-W (2560 × 1080) and the 34WR55QK-B (3440 × 1440), and ASUS lists its ProArt PA248QV as a 16:10 WUXGA (1920 × 1200) monitor. Read more in our guides to 1080p, 1440p, 4K and the 4:3 aspect ratio.
More tools
- Inches to PixelsConvert print sizes like 8.5 × 11 in to pixels at any DPI.
- Image Resolution CheckerSee any image's size, ratio and print size without uploading it.
- What's My Screen ResolutionYour screen and window size, read straight from your browser.
Frequently asked questions
- What aspect ratio is 1080x1920?
- 1080x1920 is 9:16. Divide both numbers by their greatest common divisor, 120, and you get 9 by 16. It is the vertical form of 16:9 (1920x1080), and 9:16 is the ratio Meta lists for Instagram Reels ads.
- How do I calculate an aspect ratio?
- Find the greatest common divisor of the width and height, then divide both by it. For 1920 x 1080 the divisor is 120, giving 16:9. For a decimal form, divide width by height: 1920 / 1080 = 1.78, written 1.78:1.
- How do I find the height for a 16:9 width?
- Multiply the width by 9 and divide by 16. A 1280-pixel-wide 16:9 frame is 1280 x 9 / 16 = 720 pixels tall.
- Is 21:9 really 21 to 9?
- Not exactly. 21:9 is the label monitor makers such as LG put on ultrawide screens, but a 2560 x 1080 screen reduces to 64:27 (about 2.37:1) and 3440 x 1440 reduces to 43:18 (about 2.39:1); 21:9 itself is 2.33:1.
- Does the calculator send my numbers anywhere?
- No. All the math runs in your browser. Nothing you type is sent to a server or stored.
Sources
- Recommendation ITU-R BT.709: parameter values for HDTV (1920 × 1080, 16:9), International Telecommunication Union
- Recommendation ITU-R BT.2020: parameter values for UHDTV (3840 × 2160 and 7680 × 4320), International Telecommunication Union
- aspect-ratio (CSS property), MDN Web Docs