Aspect Ratio Calculator (Simplify & Resize)
Calculate the aspect ratio from an image or video's width and height. Simplify a ratio (e.g. 1920x1080 to 16:9) or compute the missing dimension when resizing while keeping the ratio.
Common Aspect Ratios
| Ratio | Typical Use |
|---|---|
| 1:1 | Instagram square posts, social media profile pictures |
| 4:3 | Older TVs and monitors, standard photo prints |
| 16:9 | Widescreen video, HD/4K displays, the YouTube standard |
| 21:9 | Ultrawide monitors, cinematic-style footage |
| 3:2 | 35mm film cameras, the standard ratio for most digital SLR cameras |
| 9:16 | Vertical video for Instagram/TikTok Stories and Reels |
Tips
- In "Simplify Ratio" mode, enter a video resolution (e.g. 3840x2160) to reduce it by its greatest common divisor into a familiar ratio like 16:9.
- "Resize Keeping Ratio" mode is handy when creating a thumbnail and you need the resulting dimensions without distorting the original image.
- You don't need to fill in both the new width and new height — typing into one automatically clears the other, so the result is always calculated from a single target value.
- Results are rounded to the nearest whole pixel, so they may differ very slightly from the values shown in image editing software.
Frequently Asked Questions
Side Note — How aspect ratio standards came to be
The history of film aspect ratios goes back to the early 1900s. Early motion picture film was shot at a ratio close to 4:3 (precisely 1.33:1), but in the 1950s, in competition with the rise of television, cinemas began adopting wider "CinemaScope"-style formats (around 2.35:1) to offer a more dramatic viewing experience.
Television went through a similar transition. CRT televisions used 4:3 for decades, but as digital broadcasting and flat-panel TVs spread in the 2000s, 16:9 (1.78:1) became the standard for high-definition broadcasts. It's often noted that 16:9 was chosen through a mathematical compromise (a geometric mean) between the many competing widescreen film formats of the era and the older 4:3 television screen.
More recently, the rise of smartphones has given new prominence to the "tall" 9:16 ratio. Vertical video formats popularized by TikTok and Instagram Stories are optimized for how people naturally hold and watch content on a phone with one hand — a shift that challenges over a century of assumptions that video content should always be wider than it is tall.