Aspect Ratio Calculator
Aspect ratio describes the proportional relationship between an image or screen's width and height, expressed as two numbers separated by a colon (e.g., 16:9). This calculator simplifies any pair of dimensions to their lowest-term ratio by dividing both values by their greatest common divisor (GCD), so 1920×1080 reduces to 16:9 and 2560×1440 reduces to 16:9 as well.
You can also work in reverse: enter a known aspect ratio and one dimension to instantly calculate the matching second dimension. This is essential for maintaining visual proportions when resizing images, designing layouts, or configuring video output — for example, finding the correct height for a 16:9 banner that is 1200 px wide.
How it works
To simplify W:H, compute GCD(W, H) then divide: simplified ratio = (W/GCD) : (H/GCD). To scale: given ratio R_w:R_h and a known width W, height = W × (R_h / R_w). Given a known height H, width = H × (R_w / R_h).
Use cases
- Finding the simplified aspect ratio of a photo or video (e.g., 1920×1080 → 16:9)
- Calculating the correct height for a responsive banner or thumbnail at a given width
- Ensuring consistent proportions when resizing graphics for different platforms
- Determining the exact pixel dimensions for widescreen, square, or portrait video formats
- Verifying that cropped or scaled images maintain the intended aspect ratio