Aspect Ratio Calculator aspect ratio computer
Quickly calculate the aspect ratio of images, videos, screens and design drafts, and automatically reduce them to the simplest integer ratio.
Built-in commonly used ratio presets, locked ratio conversions and real-time preview.
Enter a target width or height and automatically calculate the other side (maintaining current proportions):
Automatic reduction: 1920 × 1080 → Greatest common factor 120 → 16 : 9
Lock ratio: After turning it on, modify any value and the conversion will be automatically synchronized on the other side.
Resize conversion: Enter the target width or height, maintaining proportions when calculating the other side
❓ FAQ FAQ
Frequently asked questions about aspect ratio and size conversion
What is Aspect Ratio?
Aspect Ratio It is the proportional relationship between the width and height of the image, usually expressed as an integer ratio of "width:height", for example 16:9 Represents the width as 1.78 times the height.
For example, a 1920 × 1080 For the picture, after dividing the width and height by the greatest common factor 120, we get 16 : 9。
The aspect ratio determines the image'sshow shape：
- 16:9 — Widescreen, ideal for video and TV
- 4:3 — Close to square, traditional screen and old photos
- 1:1 — Perfect circle, often seen in social posts
- 9:16 — Upright style, suitable for mobile phone portrait videos
What are the 16:9 screen resolutions?
16:9 It is currently the most mainstream display ratio. Common resolutions include:
640 × 360— nHD1280 × 720— HD（720p）1920 × 1080— Full HD（1080p）2560 × 1440— 2K / QHD（1440p）3840 × 2160— 4K / UHD7680 × 4320— 8K
Each level of resolution is twice the previous one, but the ratio is maintained at 16:9, so the same image can be enlarged without loss.
💡 Checking method: Enter any resolution into this tool, if it displays 16:9 That is the standard wide screen ratio.
What is YouTube's recommended video to thumbnail ratio?
YouTube provides support for multiple formats. The main recommendations are as follows:
Video (general): 16:9 landscape - 1920×1080 or 3840×2160 recommended
Shorts (short videos):9:16 Upright — 1080×1920 recommended
Thumbnail:16:9 — 1280×720 recommended, less than 2MB
Key points of thumbnail design:
- Thumbnails are the most important factor in determining click-through rates and account for the largest visual area of search results.
- Important text and image elements shouldstay in central safe zone, to avoid being obscured by time stamps and titles
- Use high-contrast colors and large fonts to make them legible even on small screens
What are the size rules for Instagram posts and stories?
Instagram supports multiple post formats, each with recommended sizes:
- General Post (Post):1:1 square — 1080×1080
- Portrait：4:5 — 1080×1350
- Landscape：16:9 — 1080×608
- Limited time news (Story)：9:16 — 1080×1920
- Reels:9:16 Upright — 1080×1920
💡 It is recommended to use the highest resolution version (such as 1080×1080) when uploading, Instagram will automatically compress it; uploading with a low resolution will enlarge and cause blur.
What is the ratio of TikTok videos?
TikTok withUpright 9:16 is the core ratio, the recommended upload resolution is 1080 × 1920。
Important considerations:
- TikTok is mainly displayed on the mobile phone's vertical screen, which can completely fill the screen at 9:16
- Landscape (16:9) or square (1:1) videos can also be uploaded, but will leave black bars on the top and bottom or require the user to rotate the phone
- The video length is recommended to be 21-34 seconds, and grab the audience’s attention in the first 2 seconds
- Safe area design: avoid placing important content at the bottom of the screen (it may be blocked by the interface)
💡 If you need to create straight video material, you can use the 9:16 conversion function of this tool to adjust the material of any size to the same ratio.
Why are some ratios not whole numbers (e.g. 205:78)?
Not all dimensions can be reduced to "memorable" whole-number ratios. For example, the recommended dimensions for Facebook cover images are 820 × 312, its greatest common factor is 4, and after reduction it is 205 : 78——This is its true proportion.
💡 The decimal ratio is more valuable for reference:
820 ÷ 312 ≈ 2.63 — means the width is approximately 2.63 times the height
A4（210×297）≈ 0.71 — represents a width approximately 0.71 times the height (straight)
This tool displays both the reduced integer ratio and the decimal ratio, allowing you to accurately understand the actual proportion of any size.
What browsers does this tool support? Is the data safe?
This tool is compatible with the latest versions of all major browsers:Google Chrome、Mozilla Firefox、Apple Safari、Microsoft Edge with Opera。
Privacy protection: this is a 100% pure front-end tool, all calculations are done in your browser. Entered size informationwill not be uploaded or stored Go to any server and it can be used normally even if you are offline. Please feel free to handle your work data.
📖 The Complete Guide to Aspect Ratio: From Screen to Social Media
Learn more about common proportions and sizing specifications for each platform
Function introduction
ToolHub's Aspect Ratio Calculator is a free online aspect ratio calculation tool. Enter any width and height and get it instantlyThe simplest integer ratio of automatic reduction Ratio to decimal place. It has built-in 16 commonly used ratio presets (covering screen resolutions, paper specifications, and mainstream social platforms). After turning on the locked ratio and modifying any value, the conversion will be automatically synchronized on the other side, allowing you to easily scale images, videos, and design drafts without distortion.
Common proportions
| Proportion | aspect ratio | Common uses |
|---|---|---|
| 1:1 | 1.00 | Instagram posts, avatars |
| 4:3 | 1.33 | Traditional screens, old photos |
| 3:2 | 1.50 | Single lens camera, Flickr |
| 16:9 | 1.78 | HD Video, TV, YouTube |
| 16:10 | 1.60 | MacBook, some screens |
| 21:9 | 2.33 | Ultrawide screen, movies |
| 32:9 | 3.56 | Super UltraWide screen |
| 9:16 | 0.56 | IG Story、Shorts、TikTok |
| A4 | 0.71 | ISO 216 paper (210×297mm) |
Screen ratio (16:9, 16:10, 21:9, 32:9)
16:9 It is the standard ratio for modern monitors and is used by televisions, projectors and most computer screens. Video content such as YouTube and Netflix are mainly in 16:9.16:10 Slightly higher than 16:9, commonly seen in notebook computers in the past (such as MacBook Pro 16-inch, Microsoft Surface).21:9 It is a cinema ultra-wide ratio, used for movie editing and immersive games.32:9 It is the equivalent width of two 16:9 screens spliced together, suitable for multitasking and racing simulation games.
YouTube (16:9 vs. 9:16)
General video usage on YouTube 16:9(1920×1080), while Shorts short videos Use upright 9:16(1080×1920) to comply with the habit of viewing the phone vertically. Thumbnails are fixed at 1280×720 at 16:9. If your video material is in other ratios, YouTube will display it with black borders or cropping - use this tool's locked ratio conversion to adjust the ratio of the material to the correct size first.
Instagram（1:1、4:5、9:16）
How to use square posts on Instagram 1:1(1080×1080), used for straight posts 4:5(1080×1350), limited time dynamic and Reels use 9:16(1080×1920). Choosing the correct ratio allows content to be fully represented on the timeline and avoids unnecessary cropping.
TikTok（9:16）
TikTok with 9:16 Vertical video is the core (1080×1920), completely filling the mobile phone screen. Although horizontal or square videos can also be uploaded, they will leave black borders and affect the viewing experience.
Facebook and X (Community Banner)
Facebook cover image suggestions 820×312(~205:78), X (Twitter) Banner Suggestions 1500×500(3:1). The recommended sizes for these platforms may be adjusted over time, and it is recommended to check the latest official specifications before use.
How to calculate aspect ratio?
Aspect ratio is calculated by finding the ratio of width to heightGreatest common divisor (GCD), and then divide both sides by that number:
Example: 1920 × 1080
GCD(1920, 1080) = 120
1920 ÷ 120 = 16，1080 ÷ 120 = 9
Result:16 : 9
If the two numbers have no common factors (GCD = 1), further simplification is not possible, for example 1024 × 768 The GCD is 256, which can be simplified to 4:3; while some sizes (such as Facebook cover 820×312) are still larger integers (205:78) after reduction, and the decimal ratio (2.63) is a more intuitive reference.
best practices
- Confirm the target platform ratio before exporting — Each platform has official recommended sizes. First click on the preset list and then apply it to your material.
- Make good use of lock ratios — After turning on Lock Aspect Ratio, enter the target width to get the correct height, and vice versa
- Avoid non-integer scaling — If the proportion is incorrect when scaling the image, it will cause distortion; use this tool to calculate the correct size first and then scale it.
- Keep original high-resolution files — When outputting after calculation, scale down from the highest resolution version to obtain the best image quality.
Browser compatibility
This tool is developed based on modern web standards and is compatible with the latest versions of all major browsers: Google Chrome, Mozilla Firefox, Apple Safari, Microsoft Edge and Opera. It is recommended to use the latest version for the best experience.
Privacy protection
ToolHub takes the privacy of your data seriously. Aspect Ratio Calculator adopts 100% pure front-end architecture, all calculations and conversions are completed in your browser, and the size data entered will not be transmitted, stored or shared to any external server. You can use it safely in a completely offline environment.