Aspect Ratio Calculator
Calculate, scale, and convert aspect ratios for images, videos, and screens
Enter width and height to find the simplified aspect ratio.
Simplified Ratio
Decimal Ratio
Dimensions
Enter a known ratio and one dimension to calculate the other.
Scale original dimensions to fit inside a container (letter-boxing / pillar-boxing).
Scaled Width
Scaled Height
Fit Type
Visual Preview
Rectangle preview scaled proportionally (max 200px)
Common Presets
Quick Reference
Quick Tip
Use Scale to Fit to calculate how a video or image fits inside a fixed container — the tool automatically handles letter-boxing (horizontal bars) and pillar-boxing (vertical bars).
What Is an Aspect Ratio?
Understanding the proportional relationship between width and height in images, video, and screens
An aspect ratio is the proportional relationship between the width and height of a rectangle — typically expressed as two numbers separated by a colon, such as 16:9 or 4:3. It describes the shape of an image or screen without specifying its exact size. A 1920×1080 HD video and a 1280×720 video both share the same 16:9 aspect ratio, meaning they have identical proportions at different resolutions.
Aspect ratios are fundamental in photography, videography, web design, and display technology. Choosing the wrong ratio when exporting or embedding media leads to stretching, cropping, or unwanted black bars — commonly called letter-boxing (horizontal bars top and bottom) or pillar-boxing (vertical bars on the sides).
Video & Screens
16:9 dominates modern displays. Knowing the ratio lets you export video at any resolution — 720p, 1080p, 4K — while keeping the same proportions.
Photography
Digital cameras default to 3:2 (matching 35mm film). Printing to standard sizes often requires cropping to fit different aspect ratios like 4:3 or 1:1.
Web & Social Media
Every platform has preferred ratios. Instagram favours 1:1 and 4:5, YouTube 16:9, and TikTok 9:16. Using the correct ratio avoids automatic cropping.
How to Use the Aspect Ratio Calculator
Three powerful modes for every aspect ratio task
Calculate Ratio — Find the Simplified Aspect Ratio
Enter any width and height in pixels (or any unit). The calculator uses the Greatest Common Divisor (GCD) algorithm to reduce the numbers to the simplest possible ratio. For example, 1920×1080 becomes 16:9, and 2560×1440 also simplifies to 16:9. You also see the decimal ratio (width ÷ height) for quick comparisons.
Scale Dimensions — Find Width or Height from a Ratio
Enter a known ratio (e.g., 16:9) and one dimension to calculate the other. Select whether your known value is the width or height, then enter it. Ideal for resizing images without distortion — for example, finding the correct height for a 16:9 banner that is 1200px wide (result: 675px).
Scale to Fit — Fit Media Inside a Container
Provide the original media dimensions and a target container size. The calculator scales the media as large as possible while maintaining its aspect ratio, fitting entirely within the container — exactly like the CSS object-fit: contain or video letter-box behaviour. The result tells you the scaled width, height, and whether bars will appear on the sides or top/bottom.
Use Common Presets for Instant Results
Click any preset (16:9, 4:3, 1:1, 21:9, 9:16, 3:2, 4:5, 2:3) to instantly load those values into the current mode. Presets work across all three calculator modes, so you can quickly switch between ratio calculation and dimension scaling for standard formats.
Common Aspect Ratios Explained
Understanding when and where each ratio is used
16:9 — Widescreen Standard
The universal standard for HD and 4K video. Used by YouTube, Netflix, Blu-ray, and virtually all modern monitors and TVs. Common resolutions: 1280×720, 1920×1080, 2560×1440, 3840×2160.
4:3 — Classic Standard Definition
The format of older televisions and monitors. Still used in some educational and presentation software. A 4:3 video displayed on a 16:9 screen produces vertical pillar-box bars on each side.
1:1 — Perfect Square
Made famous by Instagram. Common for profile pictures, album art, and print formats like 8×8 or 12×12. Equal width and height make composition symmetrical and balanced.
21:9 — Cinematic Ultrawide
Used in cinema and ultrawide gaming monitors. Provides an immersive field of view. A 16:9 video on a 21:9 screen produces horizontal letter-box bars at the top and bottom.
9:16 — Vertical / Portrait
The natural format for smartphones held upright. Used by Instagram Reels, TikTok, YouTube Shorts, and Snapchat. It is simply 16:9 rotated 90 degrees.
3:2 — Photography Standard
The native ratio of most DSLR and mirrorless cameras, derived from 35mm film. Standard print sizes like 4×6 and 6×9 inches match this ratio exactly.
Frequently Asked Questions
Common questions about aspect ratios and how to use this calculator