Our aspect ratio calculator helps designers, videographers, and developers work with image and video dimensions. Enter width and height to find the simplified ratio, provide a ratio and one dimension to calculate the other, or resize any resolution while maintaining its proportions. Includes quick presets for all major social media platforms and standard screen resolutions from HD to 8K.
| Name | Resolution | Ratio |
|---|---|---|
| 8K UHD | 7680×4320 | 16:9 |
| 4K UHD | 3840×2160 | 16:9 |
| QHD | 2560×1440 | 16:9 |
| Full HD | 1920×1080 | 16:9 |
| HD | 1280×720 | 16:9 |
| UW FHD | 2560×1080 | 21:9 |
| XGA | 1024×768 | 4:3 |
| Square | 1080×1080 | 1:1 |
Enter width and height in pixels to instantly calculate the simplified aspect ratio using GCD.
Select a preset ratio and enter one dimension to find the matching width or height.
Enter your current dimensions and a new width or height to resize while keeping the same aspect ratio.
The aspect ratio is found by dividing both width and height by their Greatest Common Divisor (GCD). For example, 1920x1080: GCD(1920,1080) = 120, so the ratio is 1920/120 : 1080/120 = 16:9. To find a missing dimension: Height = Width / (RatioW / RatioH), or Width = Height * (RatioW / RatioH).
Ratio = W/GCD(W,H) : H/GCD(W,H)
16:9 is the most common widescreen ratio, used for HD (1280x720), Full HD (1920x1080), and 4K (3840x2160)
4:3 was the standard ratio for older TVs and monitors — still used for presentations and some tablets
Instagram posts use 1:1 (square), while Stories and Reels use 9:16 (vertical)
YouTube recommends 16:9 for standard videos and 9:16 for Shorts
21:9 (ultrawide) is popular for cinematic content and ultrawide monitors
When resizing, always lock the aspect ratio to avoid stretching or squishing your images
3:2 is the classic photography ratio used by most DSLR cameras
Use the decimal ratio (e.g., 1.778 for 16:9) for quick mental math when scaling
Our free aspect ratio calculator helps you find the ratio from any pixel dimensions, calculate missing width or height for a given ratio, and resize images while maintaining proportions. Perfect for video editors, photographers, web designers, and social media creators.
Enter any width and height to find the simplified aspect ratio using the GCD (Greatest Common Divisor) method.
For example, 1920x1080 simplifies to 16:9, and 2560x1440 simplifies to 16:9 as well.
Our calculator also shows the decimal ratio for quick reference.
16:9 is the standard widescreen ratio used for HD, Full HD, 4K, and 8K resolutions.
Common 16:9 resolutions include:
Enter any width to instantly calculate the matching 16:9 height.
Each social media platform has recommended aspect ratios:
Use our platform presets to get the exact pixel dimensions.
Aspect ratio is the proportional relationship between an image's width and its height, written as two numbers separated by a colon, such as 16:9.
It works by expressing width and height as their smallest whole-number ratio, found by dividing both dimensions by their greatest common divisor (GCD). A 1920x1080 image has a GCD of 120, so it reduces to 16:9.
Aspect ratio is independent of resolution: 1280x720 and 3840x2160 both share the 16:9 ratio despite very different pixel counts. As the SMPTE and ITU-R BT.709 broadcast standards define, ratio governs shape while resolution governs detail, which is why the two must be considered separately when preparing media.
To find a missing dimension, multiply or divide the known dimension by the ratio's decimal value.
If you know the width and want the height for a 16:9 image, divide width by 16 and multiply by 9: a 1600px width gives 1600/16x9 = 900px. To find width from height, reverse the operation: multiply height by 16 and divide by 9.
The decimal form (16/9 = 1.778) makes scaling fast, since width always equals height times the decimal ratio. This is the same arithmetic used in CSS layout, where the aspect-ratio property documented by MDN Web Docs lets browsers reserve the correct box shape before an image loads, preventing layout shift.
Photography and film use a distinct set of aspect ratios separate from screen standards.
Most DSLR and mirrorless cameras capture 3:2 (1.5), inherited from 35mm film, while Micro Four Thirds sensors use 4:3.
Cinema relies on wider formats: 1.85:1 (flat) and 2.39:1 (anamorphic scope) are the theatrical standards defined by SMPTE, and 21:9 approximates cinematic ultrawide for home viewing.
Print sizes follow yet another logic; the ISO 216 A-series (A4, A3) uses a 1:1.414 (root-2) ratio so that halving a sheet preserves its proportions.
Knowing the source ratio prevents unwanted cropping when moving an image between camera, screen, and paper.
Changing an image's aspect ratio without stretching it requires either cropping or adding bars, never simply resizing both dimensions unequally.
Cropping trims pixels from the edges to reach the target shape, sacrificing content but filling the frame. Letterboxing (horizontal bars) or pillarboxing (vertical bars) preserves the entire image by padding the empty space, which is how broadcasters following ITU-R display standards fit 4:3 material on 16:9 screens.
Stretching, by contrast, forces mismatched dimensions and visibly distorts faces and circles.
When you must convert, decide whether content integrity (letterbox) or a full frame (crop) matters more, and calculate the exact padded or trimmed dimensions before exporting.
For web design, aspect ratio should be defined in CSS rather than fixed pixel sizes so images scale fluidly across devices.
The modern CSS aspect-ratio property, documented by MDN Web Docs and part of the W3C CSS specification, lets you declare aspect-ratio: 16 / 9 on a container, reserving space and eliminating cumulative layout shift (CLS), a Core Web Vitals metric tracked by Google.
Common web ratios include:
Always pair a declared ratio with responsive units so the same markup adapts from mobile portrait to desktop widescreen without hard-coded dimensions.
Choose a monitor aspect ratio based on your primary workload rather than defaulting to whatever is cheapest.
VESA and the display industry define these formats around common panel resolutions, so matching your content ratio to the panel avoids black bars. For mixed use, 16:10 or 21:9 generally provides the most flexible working area per dollar.
Correct aspect ratios directly affect how content appears in search results and social previews, making them a practical part of technical SEO.
Open Graph and Twitter Card previews render best at 1.91:1 for link images, and mismatched dimensions get cropped unpredictably in the feed.
In search, Google's structured-data image guidelines recommend supplying multiple aspect ratios (16:9, 4:3, and 1:1) so the engine can select the best crop for each surface. On-page, declaring image ratios prevents layout shift that harms Core Web Vitals.
Getting the ratio right at export time therefore improves both click-through appearance on social platforms and the perceived stability that ranking systems reward.
The most common aspect ratio mistake is resizing width and height independently, which stretches the image and distorts every shape within it; always lock the ratio when scaling.
Data sourced from trusted institutions
All formulas verified against official standards.