Calculate aspect ratios, resize dimensions while maintaining proportions. Common presets for video, photo, mobile screens, and social media
Lock an aspect ratio and calculate the missing dimension. Enter a width and ratio (like 16:9) to find the height, or enter both dimensions to determine the ratio. Useful for resizing images, videos, and design layouts without distortion.
Initializing in your browser…
A 1920×1080 hero image must be resized to 1280 wide without distorting it, what height keeps the ratio?
Input
1920 × 1080 → new width 1280
Result
Aspect ratio 16:9 · new size 1280 × 720
The ratio simplifies to 16:9, so locking width to 1280 forces height to 720 to avoid stretching. The tool solves for the missing dimension and names the simplified ratio, which is handy for picking standard video and screen sizes.
Lock an aspect ratio and calculate the missing dimension. Enter a width and ratio (like 16:9) to find the height, or enter both dimensions to determine the ratio. Useful for resizing images, videos, and design layouts without distortion.
Enter a width and height (defaulting to 1920x1080) and the calculator reduces them to their simplest ratio using the Euclidean GCD algorithm. Rather than running GCD on the raw integers, it first multiplies each value by 1000 and rounds (Math.round(value * 1000)), so non-integer ratios reduce correctly too: 2.35:1 Cinemascope or a decimal width stays exact instead of collapsing to a meaningless integer pair. Alongside the simplified ratio (e.g. 16:9), it shows the decimal ratio computed as width÷height to four decimal places (1920÷1080 = 1.7778), the total pixel count formatted with thousands separators, and the megapixel figure as width·height÷1,000,000 rounded to two decimals (2.07 MP for 1080p). The simplified ratio and decimal value each have their own copy button, and a visual preview box scales the entered dimensions to fit a 300px bounding square so you can eyeball the shape.
The 'Resize Keeping Ratio' section does proportional scaling locked to whichever field you type in. Entering a new width locks width mode and computes height as Math.round(newWidth ÷ ratio); entering a new height locks height mode and computes width as Math.round(newHeight × ratio). Because both results are rounded to whole pixels, extreme scale factors can drift by a pixel from the exact ratio. The result (for example 1280 × 720 from a 16:9 source) copies as a plain '1280x720' string ready to paste into an export dialog.
Fourteen named presets are grouped into Video (16:9 HD/4K, 21:9 Ultrawide, 4:3 Standard, 2.35:1 Cinemascope, 1.85:1 Widescreen), Photo (3:2 35mm Film, 4:5 Instagram Portrait, 1:1 Square, 5:4 Large Format), Mobile (9:16 Stories/Reels, 9:19.5 iPhone, 9:20 Modern Android), and Social (1.91:1 Facebook/Twitter, 2:3 Pinterest). Clicking a preset doesn't just display the ratio; it fills the inputs with a concrete 1920px width and the matching computed height (round(1920 ÷ ratio)), giving you real working dimensions. Note that this tool is ratio-math only: it never loads or processes an actual image or video file, which distinguishes it from the image and video resizers. All inputs are stored in the URL via useUrlStates, so the Share button produces a link that reopens the calculator with your exact width, height, and resize values.
Find the right height when scaling a photo to a new width while preserving proportions.
Calculate frame dimensions for standard and ultrawide aspect ratios.
That is 16:9, the standard widescreen ratio used by most monitors and TVs.
Yes. Type any two numbers separated by a colon, such as 3:2 or 2.35:1.
Every calculation runs locally in your browser. Your numbers and expressions are not transmitted or stored.