What is the difference between aspect ratio and resolution?

Resolution is the pixel count, aspect ratio is the shape. 1280x720 and 1920x1080 are different resolutions with the identical 16:9 shape, so content moves between them without cropping.

How do I find the ratio of an arbitrary size?

Divide both numbers by their greatest common divisor. For 1,600 by 1,200 the divisor is 400, giving 4:3. If the result is not a tidy pair, express it as a decimal such as 1.85:1.

Should I letterbox or crop?

Crop when the subject sits centrally and edges are expendable, which is the norm for social video. Letterbox when composition matters, such as film content on a differently shaped screen.

Do pixels have to be square?

On modern displays yes, but older broadcast formats used non-square pixels. That is why some legacy DV footage lists a 720x480 frame yet displays at 16:9.

Aspect Ratio Calculator

Calculate and convert aspect ratios

Width (px)

Height (px)

Common Presets

Quick Facts

•16:9 = HD/4K standard (1920×1080, 3840×2160)
•4:3 = classic TV/monitor ratio
•1:1 = square format
•21:9 = ultrawide cinematic

What Is an Aspect Ratio?

An aspect ratio describes the proportional relationship between width and height. It's expressed as two numbers separated by a colon (e.g., 16:9). This ratio is crucial for displays, cameras, video production, and web design to ensure content appears correctly without distortion.

Common Aspect Ratios

16:9 is the standard for HD/4K displays and YouTube. 4:3 was the standard for older TVs and monitors. 21:9 is used for ultrawide monitors and cinematic content. 1:1 is square (Instagram posts). 9:16 is vertical (mobile stories, TikTok, Reels).

Understanding the aspect ratio calculator

Aspect ratio is the relationship between width and height, and it decides whether an image is cropped, letterboxed or stretched when it moves between screens. Resizing correctly means keeping the ratio fixed and solving for the missing dimension, which is a single multiplication once you know the ratio as a decimal.

Worked examples

Height for a 1,280 px wide image at 16:9

1The ratio as a decimal is 16 ÷ 9 = 1.7778.
2Height = width ÷ ratio: 1,280 ÷ 1.7778 = 720.
3Check: 1,280 ÷ 720 = 1.7778, so the ratio holds.

720 pixels tall, giving the familiar 1280 by 720 frame.

Fitting a 4:3 photo into a 1920 by 1080 frame

1A 4:3 image at 1,080 px tall is 1,080 × 4 ÷ 3 = 1,440 px wide.
2That leaves 1,920 - 1,440 = 480 px of empty width.
3Split evenly, giving 240 px pillarboxes on each side.
4To fill instead, scale to 1,920 wide, which makes it 1,440 tall and crops 360 px of height.

Either 240 px bars on each side, or a crop of 180 px from the top and bottom.

Common ratios and resolutions

Ratio	Decimal	Example resolutions	Where used
16:9	1.778	1920x1080, 3840x2160	TV, YouTube, most monitors
9:16	0.563	1080x1920	Reels, Shorts, TikTok
4:3	1.333	1024x768, 1600x1200	Older displays, some cameras
1:1	1.000	1080x1080	Square social posts
3:2	1.500	6000x4000	DSLR photography, prints
21:9	2.333	3440x1440	Ultrawide monitors
2.39:1	2.390	4096x1716	Cinema widescreen
4:5	0.800	1080x1350	Instagram portrait

16:9 resolution ladder

Name	Resolution	Megapixels
360p	640 x 360	0.23
720p HD	1280 x 720	0.92
1080p Full HD	1920 x 1080	2.07
1440p QHD	2560 x 1440	3.69
4K UHD	3840 x 2160	8.29
8K UHD	7680 x 4320	33.18

Frequently asked questions

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This calculator is for educational and reference purposes only. Always verify critical calculations independently.