Aspect Ratio Calculator
Calculate image and video aspect ratios, find missing dimensions, and resize content without distortion. This free tool runs in your browser, includes common ratio and dimension presets, and does not require an account.
Calculate an Aspect Ratio
Enter width and height to simplify the ratio, see the decimal value, and detect orientation.
Calculations run in your browser. Invalid values such as zero, negatives, or non-numeric text are rejected.
The simplified ratio, decimal value, and orientation will appear here.
Common Dimension Presets
Choose a common size to fill the width and height fields. These are shortcuts, not limits.
Calculate Dimensions From an Aspect Ratio
Enter a known ratio and one dimension to find the missing width or height.
Calculated pixels are shown exactly, with a rounded practical size when needed.
Common Aspect Ratios
Select a ratio to fill the reverse calculator. You can still type a custom ratio.
Resize an Image or Video Without Changing Its Aspect Ratio
Enter the original size and a new width or height. The other dimension is calculated so the original proportions are preserved.
This calculation preserves the original aspect ratio so the image or video is not stretched or squashed.
The resized size, original ratio, and scale percentage will appear here.
Disclaimer
This Aspect Ratio Calculator is provided for general information, design planning, and educational purposes only. Results are calculated in your browser from the width, height, and ratio values you enter. The tool helps you simplify ratios, find a missing dimension, and resize while keeping the original proportions. It does not crop, encode, export, or process image or video files.
Pixel values are mathematical results. Some calculated sizes include decimals; a rounded practical pixel size is shown when needed. Display, print, and platform requirements can still differ by device, codec, or publishing guidelines. Web4pps does not provide design, photography, or video-production advice. Confirm important dimensions independently when they matter for print, broadcast, or a live website.
How to Use Aspect Ratio Calculator
Follow these steps to calculate an aspect ratio, find a missing dimension, or resize without distortion:
- Calculate an aspect ratio — enter width and height in pixels, then click Calculate or press Enter. The simplified ratio, decimal ratio, and orientation appear in the result panel.
- Swap width and height — use Swap Width and Height to turn a landscape size such as 1920 × 1080 into 1080 × 1920 (9:16) for vertical video.
- Find a missing dimension — choose Height or Width, enter the aspect ratio (or pick a common ratio), then enter the known dimension.
- Resize without distortion — enter the original width and height, then a new width or new height. Lock Aspect Ratio keeps the other side in proportion.
- Use presets — common ratios fill the reverse calculator; common dimension presets fill width and height. They are shortcuts, not limits.
- Copy or clear — copy the result, or press Escape in a calculator section to clear it.
You can also click Try an example to load 1920 × 1080 (16:9) and see a matching reverse and resize example.
Who should use Aspect Ratio Calculator
This free tool is for anyone who needs accurate width-to-height proportions without creating an account or uploading files.
- Web and graphic designers preparing layouts, banners, and responsive images.
- Developers setting CSS sizes, video players, and media embeds.
- Content creators and social media managers sizing posts, Stories, and Shorts.
- Video editors matching 16:9, 9:16, 21:9, and other frame sizes.
- Photographers resizing prints and web images without stretching.
- Students learning how aspect ratios and greatest common divisors work.
It is not a replacement for image-editing software, a video encoder, or a platform's official size guide. Use it to calculate dimensions, then apply those sizes in your editor or publishing tool.
What Is an Aspect Ratio?
An aspect ratio describes the proportional relationship between width and height. It is written as two numbers separated by a colon, such as 16:9. The numbers are a simplified version of the actual pixel dimensions.
A 1920 × 1080 image has the ratio 1920:1080, which simplifies to 16:9. A 1080 × 1080 profile picture is 1:1. A 1080 × 1920 vertical video is 9:16. The ratio stays the same when you scale both sides by the same factor: 1280 × 720 is also 16:9.
Why Aspect Ratio Matters
Keeping the correct ratio prevents stretching, letterboxing, and awkward crops. It affects:
- Image proportions — so photos do not look too wide or too tall.
- Video framing — so footage matches YouTube, cinema, or vertical-video layouts.
- Website layouts — so hero images, thumbnails, and cards align in a grid.
- Social media content — so posts fit feed, Stories, Shorts, and link preview frames.
- Responsive designs — so CSS and media queries keep a consistent shape across screen sizes.
- Screen displays — so content matches 16:9 TVs, 16:10 monitors, and 21:9 ultrawide screens.
Aspect Ratio Formula
The basic formula is:
Aspect Ratio = Width : Height
Then divide both numbers by their greatest common divisor (GCD) so the ratio is in lowest terms. For 1920 and 1080, the GCD is 120:
- 1920 ÷ 120 = 16
- 1080 ÷ 120 = 9
- Simplified ratio = 16:9
The decimal ratio is width ÷ height. For 1920 ÷ 1080 the decimal value is 1.7778 when rounded to four decimal places.
To find a missing height from a known ratio:
height = width × ratioHeight ÷ ratioWidth
Example: 16:9 with width 1920 → 1920 × 9 ÷ 16 = 1080.
To find a missing width:
width = height × ratioWidth ÷ ratioHeight
Example: 16:9 with height 1080 → 1080 × 16 ÷ 9 = 1920. Example: 4:3 with height 900 → 900 × 4 ÷ 3 = 1200.
How to Resize Without Distortion
Keep the original width-to-height relationship constant. If you change the width, calculate the new height from the original ratio:
newHeight = newWidth × originalHeight ÷ originalWidth
Example: 1920 × 1080 resized to width 1280 becomes 1280 × 720. The scale is 1280 ÷ 1920 = 66.67%. Another example: 4000 × 3000 resized to width 1600 becomes 1600 × 1200 and stays 4:3.
When a calculated size is not a whole pixel, the calculator shows the exact value (for example 853.33 px) and a practical rounded size (853 px) so you can choose what your editor needs.
Common Image and Video Aspect Ratios
These ratios appear often in photos, video, and web design. The calculator can match them when your dimensions are close enough, and the preset buttons can fill the ratio fields:
| Ratio | Typical use | Example sizes |
|---|---|---|
| 1:1 | Square images, profile pictures | 1080 × 1080, 1200 × 1200 |
| 4:3 | Traditional displays, photos | 1024 × 768, 1600 × 1200 |
| 3:2 | Photography | 1200 × 800, 1800 × 1200 |
| 16:9 | HD video, YouTube, modern displays | 1280 × 720, 1920 × 1080, 3840 × 2160 |
| 9:16 | Vertical video, Stories, Shorts | 1080 × 1920, 720 × 1280 |
| 21:9 | Ultrawide displays | Cinema-style widescreen frames |
| 4:5 | Instagram portrait posts | 1080 × 1350 |
| 1.91:1 | Social media/link previews | 1200 × 628 |
Frequently Asked Questions
What is the aspect ratio of 1920 × 1080?
It is 16:9.
What is the aspect ratio of 1280 × 720?
It is 16:9.
How do I calculate an aspect ratio?
Divide the width and height by their greatest common divisor to simplify the ratio.
What is the most common video aspect ratio?
16:9 is one of the most widely used video aspect ratios.
What is 9:16 used for?
9:16 is commonly used for vertical content such as mobile videos, Stories, and Shorts.
Can I resize an image without changing its aspect ratio?
Yes. Keep the width-to-height relationship constant when changing dimensions.
What is the difference between 16:9 and 9:16?
They contain the same proportional dimensions but have different orientations: 16:9 is landscape and 9:16 is portrait.
Is this aspect ratio calculator free?
Yes. You can use it as often as you like at no cost, with no account required.
Are the dimensions I enter stored?
Calculations run in your browser. See Privacy Information below for details.
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Privacy Information
The Aspect Ratio Calculator runs entirely in your browser. Width, height, and ratio values are used only on your device to compute results. Web4pps does not require an account to use this tool, and calculator inputs are not uploaded to our servers for storage. No image or video files are processed. Do not enter information you are uncomfortable keeping on your own device while using the page.
