Free Online Calculators
Enter width or height → calculate missing dimension
This calculator lets you find a missing width or height based on a known aspect ratio, such as 16:9 or 4:3. It uses simple proportion logic: width / height = ratio. Perfect for resizing images, videos, screens, or any design layout.
Take the pixel width and height of your image, video or screen and reduce both numbers by their greatest common divisor — the result is the aspect ratio. On a computer you can read the resolution in the display settings, and for a file in the image or video properties.
Divide the width by the height to get the ratio as a decimal, or divide both values by their greatest common divisor to get it in the familiar w:h form. If you only know one side plus the target ratio, multiply or divide that side by the ratio to get the missing dimension.
Yes, 1280x720 reduces exactly to 16:9. It is the standard HD (720p) widescreen resolution.
No, 1080x1350 is a pixel resolution; its aspect ratio is 4:5. The ratio describes the shape, the resolution describes the actual pixel count.
Yes in terms of proportions, but rotated: 1080x1920 is the vertical (portrait) version of the 16:9 shape, while 1920x1080 is the landscape version. Both have identical side proportions, only the orientation differs.
Yes, 1080x1350 has exactly a 4x5 aspect ratio. 4:5 is the shape, 1080x1350 is one specific resolution with that shape.
No, 1920x1080 is 16:9 widescreen, not 4:3. A 4:3 image is noticeably squarer, as on older TVs and monitors.
A 4x5 aspect ratio is a portrait format where the height is one quarter greater than the width. It comes from large-format photography and is widely used for vertical social media posts and print sizes.
No, 4:5 and 3:4 are different portrait ratios — 4:5 is slightly closer to square, 3:4 is a bit taller relative to its width. Cropping from one to the other will cut off part of the image.
Whether you're designing a YouTube thumbnail, setting up a video export, or cropping an image for a website, getting the aspect ratio right is essential. An aspect ratio defines the proportional relationship between width and height — so a 16:9 ratio means for every 16 units of width, there are 9 units of height. Miss that balance and your visuals end up stretched, cropped awkwardly, or letterboxed in ways you didn't intend.
This calculator takes the guesswork out of the equation. Enter any two values — the ratio and one dimension — and it instantly returns the missing measurement. For example, if you know your video needs to be 1920 pixels wide in a 16:9 format, the calculator tells you the height should be exactly 1080 pixels. It also works in reverse: know the height, get the width. It handles standard ratios like 16:9, 4:3, 21:9, and 9:16, plus any custom ratio you define.
Beyond just width and height, this tool shows you the total megapixel count of the resulting resolution. A 3840×2160 frame (4K UHD at 16:9) works out to roughly 8.3 megapixels. That's useful when you're planning storage, choosing a camera setting, or optimizing images for web performance. A 4-megapixel image might be perfectly fine for a blog header but fall short for a print poster.
The calculator also surfaces common reference resolutions so you can instantly compare your custom dimensions to industry standards. If you type in a 16:9 ratio with a width of 1280, you'll see it maps to 720p HD — a widely used standard for streaming and video calls. Targeting 2560×1440? That's 1440p, also called QHD, popular among content creators and monitor manufacturers. Having these benchmarks visible helps you make informed decisions without needing to memorize every resolution standard.
For vertical video formats — like 9:16 used on TikTok, Instagram Reels, and YouTube Shorts — the calculator flips the orientation automatically. A 1080×1920 output at 9:16 gives you a full HD vertical frame, which is exactly what these platforms recommend for maximum quality and no cropping.
This tool is genuinely useful across a wide range of workflows. Video editors use it to match output settings to their timeline sequence. Web developers use it to calculate image container sizes that won't distort photos on responsive layouts. Graphic designers use it when scaling mockups across different device screens — from a 4:3 iPad display to a 21:9 ultrawide monitor.
You can also use it to check whether a custom crop will preserve quality. Say you have a 5000×3333 photo and need it at exactly 1920 pixels wide — enter the 3:2 aspect ratio and your target width, and you'll get 1280 as the correct height. No manual math, no spreadsheets. Simple-calculator.online keeps this process fast and straightforward for anyone working with digital media.
16:9 is the standard for most modern video content, including YouTube, Netflix, and broadcast TV. It corresponds to resolutions like 1280×720, 1920×1080, and 3840×2160.
Divide the width by 16, then multiply by 9. For a 2560-pixel-wide frame: 2560 ÷ 16 × 9 = 1440 pixels tall.
Square posts use 1:1, portrait posts use 4:5, and Stories or Reels use 9:16. Each format has different recommended pixel dimensions depending on the placement.