Find an aspect ratio, calculate a missing dimension, or scale dimensions while keeping the ratio locked.
1. Dimensions → Aspect Ratio
simplified aspect ratio
Decimal ratio (W÷H)
Nearest common ratio
Orientation
2. Ratio + Known Dimension → Missing Dimension
:
missing dimension
Width
Height
Ratio used
3. Scale Dimensions
scaled dimensions
New Width
New Height
Scale factor
Common Aspect Ratios Reference
Ratio
Decimal
Common Use
16:9
1.778
HD video, monitors, YouTube
4:3
1.333
Old TV, iPad, standard monitor
1:1
1.000
Instagram square, profile photos
21:9
2.333
Ultrawide monitors, cinema
3:2
1.500
DSLR photos, 35mm film
9:16
0.5625
Mobile video, Stories, TikTok
2:1
2.000
Panoramic photos, Twitter header
5:4
1.250
Old monitors (1280×1024)
Frequently Asked Questions
What is aspect ratio?
Aspect ratio is the proportional relationship between the width and height of an image, video, or screen. It is expressed as two numbers separated by a colon, such as 16:9 or 4:3. A 16:9 ratio means the width is 16 units for every 9 units of height. Aspect ratio is independent of the actual pixel dimensions — a 1920×1080 video and a 3840×2160 video both have a 16:9 aspect ratio.
What is the most common aspect ratio for video?
The most common aspect ratio for video today is 16:9 (widescreen), which is used by YouTube, most streaming services, HDTVs, and computer monitors. This replaced the older 4:3 ratio used by standard-definition TV and early computer monitors. For social media Stories and mobile video, 9:16 (vertical/portrait) is now very common. Cinematic films often use 21:9 (ultrawide) or 2.39:1 for an even wider cinematic look.
How do I maintain aspect ratio when resizing?
To maintain the original aspect ratio when resizing, scale both width and height by the same factor. If you know the original width and height, the formula is: New Height = New Width × (Original Height / Original Width), or New Width = New Height × (Original Width / Original Height). For example, if you have a 1920×1080 image and want it 800px wide, the height should be 800 × (1080/1920) = 450px. The Scale Dimensions tool above does this automatically.