Aspect Ratio Calculator

What an aspect ratio is

An aspect ratio describes the relationship between an image or screen’s width and its height, written as two numbers separated by a colon — like 16:9. It doesn’t fix the actual size, only the shape. A 16:9 image can be 1280×720, 1920×1080, or 3840×2160; all three have the same proportions, so none of them look stretched or squashed.

How to resize without distortion

The trick to resizing is keeping the ratio constant. Pick your target ratio, then set just one dimension — the calculator solves for the other so the proportions stay locked. Change the width and the height follows; change the height and the width follows. The formula is simply:

• New height = width × (ratio height ÷ ratio width)
• New width = height × (ratio width ÷ ratio height)

For example, at 16:9 a width of 1280 px gives a height of 1280 × 9 ÷ 16 = 720 px.

Common aspect ratios

• 16:9 — standard for HD/4K video, YouTube, and most monitors and TVs.
• 4:3 — older displays, many presentations, and some photography.
• 3:2 — classic 35 mm photography and many mirrorless cameras.
• 21:9 — ultrawide monitors and cinematic video.
• 1:1 — square, used for profile pictures and some social posts.
• 9:16 — vertical video for phones, Reels, Shorts, and TikTok.

The simplified ratio

The tool also shows the simplified ratio of whatever width and height you enter, reducing it by the greatest common divisor. So 1920×1080 simplifies to 16:9, and 1366×768 shows as roughly 16:9 once rounded. This is handy for checking what ratio an odd resolution actually is.

FAQ

Why does my photo look stretched?

Almost always because the width and height were changed by different amounts, breaking the ratio. Lock the ratio and solve for one dimension to avoid it.

Can I use it for video?

Yes — set 16:9 (or 9:16 for vertical) and enter your target width to get the matching height in pixels.

Is this aspect ratio calculator free?

Yes, it is completely free with no sign-up, no watermark, and no limits on how many calculations you run. Use it as often as you like for resizing photos, video, and screen layouts.

Does it run in my browser or upload anything?

All the math runs locally in your browser using plain arithmetic, so nothing is sent to a server. The calculator works with the numbers you type and never uploads your images or files.

Will the result always be a whole number of pixels?

Not always — a clean ratio applied to an odd dimension can produce a fractional pixel value. Round to the nearest whole pixel; a one-pixel difference is invisible and will not noticeably distort the image.

Does it work on a phone?

Yes, the calculator is responsive and works on phones, tablets, and desktops. You can quickly check ratios on mobile while editing photos or planning a video shoot.