tigtools

Aspect Ratio Calculator

Enter a ratio and one side to get the other, or enter a width and height to find their ratio.

Runs in your browser No sign-up

Resize to a ratio

Common ratios

px
px
aspect-ratio: 16 / 9;

Find the ratio of a size

Ratio
16:9
Decimal
1.7778:1
Closest common ratio
16:9

How to use it

  1. To resize, enter the ratio (for example 16 and 9) or pick a common one, then type a width or a height. The other side is calculated.
  2. To find a ratio, enter the width and height of an image, screen or video.
  3. Check the preview and copy the CSS aspect-ratio rule if you need it for a web layout.

How it works

Proportional resizing uses height = width × ratio height ÷ ratio width (and the reverse). Pixel sizes are usually whole numbers, so the result can be rounded; when a ratio does not divide evenly, such as 16:9 at a width of 1000, the rounded height (563) is a close approximation rather than an exact match.

A size is simplified by dividing both sides by their greatest common divisor: 1920 and 1080 share 120, giving 16:9. Some real sizes do not reduce to a familiar ratio. 1366×768 is exactly 683:384, which is very close to 16:9, so the tool also shows the closest common ratio when it is within 2 %. Likewise, “21:9” monitors are really 64:27 (2560×1080) or 43:18 (3440×1440); 21:9 is a marketing name.

In CSS, aspect-ratio: 16 / 9 makes an element keep that shape as its width changes, which is useful for video embeds and image placeholders that should not shift the layout while loading.

Examples

Video thumbnail size

A 16:9 thumbnail that must be 1280 pixels wide needs to be 720 pixels high.

Identifying a screen's ratio

2560×1600 simplifies to 8:5, which is the same as 16:10, common on laptops.

Portrait crop for social media

With a 4:5 ratio and a width of 1080, the height is 1350, a portrait size many feeds accept.

Frequently asked questions

Is 16:9 the same as 1.78:1?

Yes. 16 ÷ 9 ≈ 1.778, so the two describe the same shape. Cinema formats are often given as decimals, such as 2.39:1.

Why does my result have decimals?

Not every width divides evenly by the ratio. Turn on rounding for pixel sizes; the result is then the nearest whole pixel, which may be a fraction of a pixel off the exact ratio.

Does the CSS aspect-ratio property work everywhere?

It is supported in all current major browsers. If an element also has both width and height set explicitly, those take priority over aspect-ratio.

Privacy

All calculations run in your browser. Nothing is sent or stored.