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Aspect Ratio Calculator

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How to Use This Calculator

Step 1: Pick a mode — *Find Aspect Ratio* (get the ratio of any width × height), *Resize an Image* (enter your original size and one new dimension to get the other without distortion), or *Resize to Ratio* (fit a known ratio like 16:9 to one dimension).

Step 2: Choose your unit — pixels, inches, cm, or mm — then enter the values for your mode, e.g. an original 712 × 430 image and a new width of 500.

Step 3: Click Calculate. You get the exact ratio, the nearest standard ratio (16:9, 4:3, 5:3…), and the resized dimensions.

What Is Aspect Ratio?

Aspect ratio is width-to-height proportion (W:H). 16:9 = 16 units wide per 9 tall.

Most displays are 16:9. Social media varies: Instagram 1:1 or 4:5, Stories 9:16, YouTube 16:9. Wrong ratios cause letterboxing or distortion.

Formulas

Find Ratio: GCD(width,height), divide both.
1920x1080: GCD=120. 1920/120:1080/120 = 16:9

Resize: Height = Width x (RatioH/RatioW)
1280 at 16:9: Height = 1280x9/16 = 720

Common Ratios

RatioDecimalUse
1:11.0Instagram posts
4:31.333Old TVs, iPad
3:21.5DSLR photos
16:91.778HD/4K, YouTube
21:92.333Ultrawide monitors
9:160.5625Stories, Reels
4:50.8Instagram portrait

Examples

Example 1: 1920x1080 = 16:9

Example 2: 1:1 at 1080px = 1080x1080

Example 3: 3:1 at 1200px wide = Height 400px

Tips

Match the platform. YouTube 16:9, Instagram 1:1 or 4:5, Stories 9:16.

Crop, do not stretch. Stretching distorts content.

All HD/4K = 16:9. 1920x1080, 2560x1440, 3840x2160.

CSS aspect-ratio property for responsive layouts.

Frequently Asked Questions

What aspect ratio is 1920x1080?
1920 by 1080 pixels is a 16:9 aspect ratio, which is the standard for HD television, computer monitors, and online video. This ratio was adopted because it closely matches the natural human field of vision. 4K resolution (3840x2160) is also 16:9 — exactly double the dimensions in both directions, which makes upscaling straightforward.
What is the best aspect ratio for YouTube videos?
YouTube's standard player uses 16:9, so videos at 1920x1080 (1080p) or 3840x2160 (4K) display perfectly without any black bars. If you upload a video with a different ratio, YouTube will automatically add black bars (letterboxing or pillarboxing) to fill the remaining space. For YouTube Shorts, use 9:16 (1080x1920) — the vertical format optimized for mobile viewing.
How do I find the aspect ratio of my image or video?
Enter the pixel width and height into the calculator. You can find these dimensions by right-clicking the file and selecting Properties (Windows) or Get Info (Mac). In most image editors, the dimensions appear in the title bar or under Image > Canvas Size. For video files, right-click and check Properties > Details tab, or open the file in VLC and go to Tools > Media Information.
What is the golden ratio and how is it used in design?
The golden ratio is approximately 1.618 to 1 (often represented by the Greek letter phi). It appears frequently in nature, art, and architecture and is considered aesthetically pleasing. Photographers use it for composition (similar to the rule of thirds but slightly different placement). It is not a standard screen or video ratio, but some designers use it when creating layouts, logos, and page proportions.
Can I use this calculator for print dimensions?
Yes. Aspect ratio is a pure proportion — it works the same regardless of the unit. Enter dimensions in pixels, inches, centimeters, or any consistent unit. A 6 by 4 inch photo has the same 3:2 aspect ratio as a 6000 by 4000 pixel digital image. This makes the calculator useful for print design, poster sizing, and photo cropping as well as digital media.
What if the width and height have no common factor?
The calculator divides both dimensions by their greatest common divisor (GCD) to simplify. If the GCD is 1 (no common factor other than 1), the ratio is returned as the original numbers — for example, 1366x768 simplifies to 683:384, which is not a standard ratio. This happens because 1366x768 is a slightly imprecise approximation of 16:9 used by some laptop manufacturers to save manufacturing costs.

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