Free tool

Aspect Ratio Calculator

Get the other side in pixels for any aspect ratio, custom ones included, or find the ratio of any size. Presets for YouTube, Instagram and TikTok.

Looked after by Set, a set square.

1. Pick a ratio

16:9: YouTube, TV, Most Videos

2. Enter a dimension

Quick pick

Result

16:9

Width

1920px

Height

1080px

Social media presets

Tap one to fill in the calculator.

Common ratios

16:9

Widescreen · YouTube, TV, Most Videos

9:16

Vertical · TikTok, Reels, Shorts

4:3

Standard · Old TV, iPad, Presentations

1:1

Square · Instagram Posts, Profile Pics

21:9

Ultra-wide · Cinema, Ultrawide Monitors

2.39:1

Anamorphic · Hollywood Films

4:5

Portrait · Instagram Portrait

3:2

Classic Photo · DSLR Photos, 35mm Film

Standard video resolutions

How it works

  1. 1Pick a ratio16:9 for YouTube, 9:16 for Reels and TikTok.
  2. 2Enter one sideWidth or height, in pixels.
  3. 3Read the otherCalculated to keep the proportions exact.
  4. 4Copy the sizePaste it into your export settings.

Questions

What aspect ratio is 1920x1080?
1920x1080 is 16:9, which is 1.78:1 as a decimal. 1280x720, 2560x1440, 3840x2160 (4K UHD) and 7680x4320 (8K) are all 16:9 too. Flipped, 1080x1920 is 9:16, the vertical size for Shorts, Reels and TikTok.
How do I work out a 16:9 size?
Height = width x 9 / 16, and width = height x 16 / 9. So 1920 wide is 1080 high, and 2160 high is 3840 wide. Pick 16:9 in the calculator, type either side, and it gives you the other.
Is 16x9 the same as 16:9?
Yes. 16x9, 16:9 and 16/9 all mean 16 units wide for every 9 tall. You can type any of them in the custom ratio box.
What if my size does not reduce to a neat ratio?
Some sizes do not. 1366x768 reduces to 683:384, which is really 16:9 to within a fraction of a percent. 2560x1080, sold as 21:9, is actually 64:27, or 2.37:1. The Find the ratio mode shows the exact ratio, the decimal and the nearest standard ratio, so you can tell.
How do I change the aspect ratio without stretching?
Keep the proportions: change one side and let the calculator give you the other. Going from one ratio to another, say 16:9 to 9:16, you either crop (lose the edges) or pad (add bars). You never stretch, which distorts faces and text.
What is aspect ratio?
Aspect ratio is the proportional relationship between the width and height of an image or video. It's expressed as two numbers separated by a colon (e.g., 16:9). A 16:9 aspect ratio means for every 16 units of width, there are 9 units of height.
What aspect ratio is best for YouTube?
YouTube recommends 16:9 aspect ratio for standard videos (1920x1080 or 1280x720). For YouTube Shorts, use 9:16 vertical format (1080x1920). YouTube will add black bars (letterboxing/pillarboxing) if your video doesn't match 16:9.
What aspect ratio is TikTok and Instagram Reels?
TikTok and Instagram Reels both use 9:16 vertical aspect ratio, with recommended dimensions of 1080x1920 pixels. This fills the entire phone screen when viewed in portrait mode.
How do I calculate aspect ratio from dimensions?
Divide both width and height by their greatest common divisor (GCD). For example, 1920x1080: GCD is 120, so 1920÷120=16 and 1080÷120=9, giving you 16:9. Our calculator does this automatically.
What's the difference between 16:9 and 4:3?
16:9 is widescreen format used by modern TVs, YouTube, and most video content. 4:3 is the older "standard" format from traditional TV and early computer monitors. 16:9 is wider and more cinematic, while 4:3 is more square-shaped.
What aspect ratio do movies use?
Most Hollywood films use either 2.39:1 (anamorphic widescreen) or 1.85:1 (standard widescreen). IMAX films often use 1.43:1. The 2.39:1 ratio gives the classic "cinematic letterbox" look when viewed on a 16:9 screen.
What is aspect ratio?

Aspect ratio is the relationship between width and height. 16:9 means 16 units wide for every 9 units tall.

Why it matters

The wrong ratio means black bars, cropping, or a stretched picture. Every platform expects its own dimensions.

How to use this calculator

Choose the ratio you are delivering, enter one dimension, and the calculator gives you the other so the proportions hold.

Related research and guides

This tool is looked after by Set.Straight-laced. Every angle checked, twice.

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