Orpheus

Aspect Ratio Calculator

Keep proportions when resizing, and name the ratio.

Inputs
px
px
px
New height
720px
Ratio
16:9 (widescreen)
Decimal ratio
1.7778
Exact new height
720.00px
Megapixels at new size
0.92MP
new height = new width × (original height ÷ original width)

Every tool runs entirely in your browser. Your files are never uploaded to a server.

To resize proportionally, multiply the new width by the original height divided by the original width. A 1920×1080 image at 1280 wide becomes 720 tall, because both are 16:9.

How to use Aspect Ratio Calculator

  1. Enter the original size. Width and height in pixels.
  2. Enter the new width. The height that preserves the proportions is calculated.
  3. Check the ratio. Common ratios are named; anything else is reduced to lowest terms.

About calculating aspect ratio

Aspect ratio is shape rather than size, and keeping it constant is the difference between resizing and distorting. The arithmetic is a single multiplication, and the errors come from two places. The first is rounding: pixel dimensions must be integers, so any target width that does not divide cleanly produces a fractional height, and rounding it shifts the ratio very slightly. Usually that is invisible; occasionally, in a tiled layout or a video encoder that demands dimensions divisible by two or by sixteen, it is not. Choosing widths that are multiples of the ratio removes the problem, which is why standard sizes cluster on numbers like 1280, 1600 and 1920. The second error is cropping confused with scaling. Changing an image from 16:9 to 1:1 is not a resize at all — some of the picture has to go, and which part is a decision nobody but you can make. Automated crops take the centre, which is wrong for most photographs of people. And a note on video specifically: pixels are not always square. Some broadcast formats use non-square pixels, so the stored resolution and the displayed shape genuinely differ, which is why a file can be 720×576 and still display as 16:9.

Frequently asked questions

What does 16:9 actually mean?
That the width is 16 units for every 9 of height — a ratio, not a size. 1920×1080, 1280×720 and 3840×2160 are all 16:9. It became the television and video standard because it sits roughly between the old 4:3 and the widest cinema formats.
Why does my resized image look slightly squashed?
Because the exact height was fractional and got rounded. Resizing 1920×1080 to 1000 wide gives 562.5, and rounding to 562 or 563 shifts the ratio a fraction of a percent. Choosing widths divisible by the ratio avoids it entirely.
What ratio should I use for social video?
Vertical 9:16 for stories and short-form, square 1:1 for feed posts that must work everywhere, and 16:9 for landscape video. Shooting 16:9 and cropping to 9:16 loses most of the frame, so it is worth deciding before filming rather than after.
Is aspect ratio the same as resolution?
No. Resolution is the pixel count; ratio is the shape. Two images can share a ratio at wildly different resolutions, and two images at the same resolution can have different ratios only if one is not what it claims to be.

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