liminfoAspect Ratio Calculator
Free web tool: Aspect Ratio Calculator
Aspect Ratio
16:9
Decimal
1.7778
Total Pixels
2.07 MP
Resize Calculator
Common Aspect Ratios
About Aspect Ratio Calculator
The Aspect Ratio Calculator helps designers, developers, videographers, and content creators instantly determine the aspect ratio of any width-height combination and scale dimensions while maintaining proportions. Enter any width and height — for example, 1920×1080 — and the tool instantly calculates the simplified ratio (16:9), the decimal representation (1.7778), and the total pixel count (2.07 megapixels).
The resize calculator section lets you scale an image or frame to a new size while preserving the original ratio. Enable "Lock ratio" to automatically calculate the missing dimension: enter a new width and the height updates instantly, or vice versa. This is essential for web development, video production, and print design where maintaining exact proportions prevents image distortion.
The tool includes a visual preset gallery of 12 common aspect ratios: 1:1 (square, Instagram), 4:3 (classic TV/monitors), 3:2 (photography), 16:9 (widescreen HD), 16:10 (laptops), 21:9 (ultrawide), 32:9 (super ultrawide), 9:16 (portrait/TikTok), 4:5 (Instagram portrait), 2:3 (portrait photography), 2.39:1 (anamorphic cinema), and 1.85:1 (cinema flat). Each preset is shown with a proportional visual rectangle for immediate recognition.
Key Features
- Automatic ratio simplification using the Greatest Common Divisor (GCD) algorithm
- Decimal ratio output (e.g., 1.7778 for 16:9) for use in CSS and programming contexts
- Total megapixel count calculated from width × height for resolution comparison
- Resize calculator that auto-fills the missing dimension when ratio lock is enabled
- 12 visual aspect ratio presets including 16:9, 4:3, 21:9, 9:16, 2.39:1 (anamorphic), and 1.85:1
- Proportional rectangle preview for each preset to visually identify ratios at a glance
- Preset detection — active preset is highlighted blue when your input matches a common ratio
- 100% client-side processing — all calculations happen in the browser with no data sent to a server
Frequently Asked Questions
What is an aspect ratio?
An aspect ratio is the proportional relationship between the width and height of a display, image, or frame, expressed as two numbers separated by a colon (e.g., 16:9). It defines the shape of the image without specifying its actual size. The same 16:9 ratio applies to a 1280×720 thumbnail and a 3840×2160 4K display.
How is the aspect ratio calculated from width and height?
The simplified aspect ratio is found by dividing both the width and height by their Greatest Common Divisor (GCD). For example, 1920 and 1080 share a GCD of 120, so 1920÷120 = 16 and 1080÷120 = 9, giving the ratio 16:9. The decimal ratio is simply width ÷ height (1920 ÷ 1080 ≈ 1.7778).
How do I resize an image while keeping the aspect ratio?
Use the "Resize Calculator" section and enable "Lock ratio". Enter a new width and the height will automatically update to maintain the original proportions. For example, scaling a 1920×1080 image to a width of 960 will automatically set the height to 540, preserving the 16:9 ratio.
What is the difference between 16:9 and 16:10?
16:9 (decimal 1.778) is the standard widescreen format used in HD TVs, most monitors, and YouTube videos. 16:10 (decimal 1.6) is slightly taller and was common in older laptops and MacBook Pros. The difference is subtle but noticeable — a 16:10 image would appear letterboxed on a 16:9 display.
What aspect ratio is used for TikTok and Instagram Reels?
TikTok, Instagram Reels, and other short-form vertical video platforms use a 9:16 aspect ratio (the inverse of 16:9 widescreen). This corresponds to portrait orientation on a smartphone. Instagram also supports 4:5 for portrait posts, which is slightly wider than 9:16 and fills more of the feed.
What is 2.39:1 (anamorphic) aspect ratio?
2.39:1 is the anamorphic widescreen format used in theatrical cinema. Films shot in this format appear as a very wide letterboxed image (sometimes called "Cinemascope"). It creates the distinctive "black bars" at the top and bottom when viewed on a standard 16:9 display. The ratio 2.39:1 is internally stored as 239:100 for precise GCD calculation.
How do I find the aspect ratio of a non-standard resolution?
Enter any width and height values into the Width and Height fields. The calculator immediately computes the simplified ratio using GCD reduction. For example, entering 2560×1440 gives 16:9 (since both divide by 160), while 2560×1600 gives 8:5 (equivalent to 16:10).
What does "megapixels" mean in the context of this calculator?
Megapixels (MP) is the total number of pixels in an image, calculated as width × height ÷ 1,000,000. A 1920×1080 image has 1920 × 1080 = 2,073,600 pixels, or approximately 2.07 MP. Higher megapixel counts mean more detail but also larger file sizes. The MP figure helps compare resolution sizes at a glance.