ToolnozaRead width before height
An aspect ratio is width:height, not a pixel count. A 1920 × 1080 image has the same 16:9 ratio as a 1280 × 720 image. A portrait 1080 × 1920 image is 9:16 instead.
Reduce the ratio
Divide both dimensions by their greatest common divisor. For 1920 and 1080, divide by 120 to get 16:9. For 1200 × 1500, divide by 300 to get 4:5.
Find a matching size
To keep 16:9 at a width of 1200 pixels, calculate height = 1200 × 9 ÷ 16 = 675 pixels. Enter the original dimensions in the calculator, then use the image resizer to produce the actual file.
Cropping or stretching?
Changing a square image to 16:9 requires a choice: crop part of the image, add empty space, or distort it. Resizing both sides independently stretches the subject. Preserve the ratio when the whole composition must remain intact.
Check the exported image
Confirm width and height after downloading. Integer pixel dimensions sometimes require rounding, so a near-match may not be exact. Aspect ratio alone says nothing about sharpness, compression or file size; inspect those separately.