Calculate and convert aspect ratios. Enter any 3 of 4 values to auto-calculate the fourth, keep dimensions proportional, and preview the result.
Free online aspect ratio calculator for images, video, screens, and responsive layouts.
Enter any 3 values to calculate the fourth dimension and keep the ratio proportional.
Fill any three fields to auto-calculate the missing dimension.
Simplified: — · Decimal: —
Enter the original width and height, then type only the new width or the new height. The calculator fills the missing side automatically.
If you know the new width you need for a layout, banner, or embed, enter it and let the tool calculate the matching height.
Start from a preset like 16:9 or 4:3, then test target sizes for video exports, social media assets, and responsive designs.
Enter any 3 values and calculate the missing width or height while preserving the same aspect ratio.
Start from common formats like 16:9, 4:3, 1:1, 21:9, and vertical social-video ratios.
Check the resulting shape visually before you resize an image, video frame, or screen layout.
Enter the original width and height first when you know them. That gives the calculator a clean baseline before you change the output size.
For proportional resizing, enter either the new width or the new height, not both. That lets the tool preserve the aspect ratio automatically.
The preview helps you confirm whether the final shape looks like a widescreen frame, a square crop, a vertical video, or a more unusual format before export.
This aspect ratio calculator is built for the common real-world case where you know three values and need the fourth without distorting the image or frame. Enter the original width and height plus one target dimension, and the calculator can derive the missing side automatically. That makes it useful for image resizing, video export planning, responsive embeds, and screen mockups. Because aspect ratio is only the relationship between width and height, the same math works whether you are resizing a 1920 by 1080 video, creating a square social post, or checking how an ultrawide banner should scale. The tool should help users get an answer immediately above the fold, then understand why the ratio matters further down the page.
Some aspect ratios show up so often that they have become shorthand for specific types of media. A 16:9 ratio is the modern default for video, YouTube, TVs, and most presentation slides. A 4:3 ratio is older but still relevant for legacy displays, some tablet layouts, and archived media. A 1:1 square ratio is common for profile images and square social posts. A 21:9 ratio is associated with ultrawide monitors and cinematic framing. A 3:2 ratio is still common in DSLR photography, while 9:16 dominates mobile-first video on platforms like TikTok, Shorts, and Reels. The point of an aspect ratio converter is not only to label these formats, but to help users move between them without stretching content or guessing dimensions manually.
Different platforms reward different aspect ratios, and choosing the wrong one can lead to black bars, awkward cropping, or reduced visual impact. YouTube is still most comfortable at 16:9. Instagram supports multiple shapes, but 1:1, 4:5, and 9:16 are especially common depending on whether the content is a feed post, story, or reel. TikTok and most short-form vertical video workflows are built around 9:16. X, paid social placements, and ad networks can have their own preferred dimension ranges too, which is why a video aspect ratio calculator is often used before export rather than after publishing. If a creator or marketer can quickly test what happens when width changes but the ratio must stay consistent, they can avoid distortion and re-rendering mistakes.
Display aspect ratio is the visible relationship between width and height on screen, such as 16:9 or 4:3. Pixel aspect ratio is slightly different. It describes the shape of individual pixels themselves. Most modern web workflows assume square pixels, which makes the two concepts feel almost identical in daily use. But in some video and broadcast workflows, pixels may not be perfectly square, which can change how footage appears when displayed. For most web users, designers, and developers, the practical need is the display ratio, because that is what controls layout, embeds, and exported frame size. Still, understanding the difference helps explain why some older footage can look stretched even when the numeric dimensions seem familiar.
The safest way to resize an image or video is to lock the aspect ratio and change only one target side at a time. If you adjust both width and height freely, the content can stretch and faces, products, or interface elements will look wrong. That is why a proportional resize calculator is useful: it preserves the original relationship automatically. Start with the source dimensions, decide which output side matters most, and let the missing value calculate from the ratio instead of guessing it by eye. If you also need to fit content into a different frame, remember that preserving ratio often means accepting padding, cropping, or letterboxing. A ratio calculator does not replace design judgment, but it does remove the most avoidable math errors.
An aspect ratio calculator helps you keep width and height proportional by calculating a missing dimension from the other values.
Divide width by height to get the decimal form, or reduce both values by their greatest common divisor to get the simplified ratio like 16:9.
Yes. That is the main purpose of this calculator. If three valid values are present, the remaining value can be calculated to preserve the same ratio.
1920 by 1080 simplifies to 16:9.
The standard YouTube video aspect ratio is 16:9.
Vertical short-form video usually uses 9:16.
Aspect ratio is the relationship between width and height, while resolution is the actual pixel count for those dimensions.
Yes. Keeping the aspect ratio constant is the key step for resizing without distortion.