Aspect Ratio Calculator

Work out a ratio from width and height, or solve for a missing width or height when you already know the ratio. Includes the nearest standard ratio match and diagonal length.

Find Aspect Ratio Find Width Find Height

Well-Known Ratio

Aspect Ratio

:

Width

Height

Units

Answer

Aspect ratio 16:9

Actual (decimal) 1.78:1

Nearest standard 16:9

Width 1920 px

Height 1080 px

Width / Height 1.7778

Diagonal 2202.9 px

16:9

How to Calculate Aspect Ratio

Aspect ratio is simply the relationship between how wide something is and how tall it is. There are two common ways to express it once you know the width and height.

Method 1 — as a decimal

Divide the width by the height. Whatever number you get is the ratio of width to a height of 1, written as "that number : 1". For a 1920 × 1080 screen, 1920 ÷ 1080 = 1.777…, which rounds to 1.78:1.

Method 2 — as whole numbers

Find the greatest common factor (GCF) of the width and height, then divide both by it. For 1920 × 1080, the GCF is 120: 1920 ÷ 120 = 16, and 1080 ÷ 120 = 9. That gives the familiar whole-number ratio 16:9 — the same shape as 1.78:1, just written differently.

Once you have a ratio, you can go the other way too: given a target width, multiply it by (height ÷ width) of the ratio to get the matching height, or vice versa. That's exactly what the "Find Width" and "Find Height" modes above do for you automatically.

Why Aspect Ratio Matters

Screens, images and video frames all come in different shapes, and content has to be sized to fit each one correctly. Resize an image without preserving its ratio and it will look stretched, squashed, or you'll lose part of the picture to cropping.

It also matters for publishing: platforms like YouTube, TikTok, Instagram, LinkedIn and Snapchat each have preferred or required ratios for video and image posts. Get it wrong and your content may be cropped, letterboxed, or shrunk down by the platform.

The same logic applies to advertising creative — banner ads, tower ads, and square units all have their own expected ratios, so checking the target platform's spec sheet before you design is worth the two minutes it takes.

Standard Aspect Ratios

Common ratios used across displays, photography and video, sorted by width/height value. Tap any row's ratio into the calculator above to explore it further.

Ratio (W:H)	Width	Height	W/H	Typical use
9:16	9	16	0.563	Vertical / mobile video (TikTok, Reels, Shorts)
3:4	3	4	0.75	Portrait photos, tablet portrait
1:1	1	1	1	Square posts, profile avatars
5:4	5	4	1.25	Older monitors, some print formats
4:3	4	3	1.333	Classic TV and CRT monitors
3:2	3	2	1.5	35mm and DSLR photography
14:9	14	9	1.556	Broadcast compromise ratio
16:10	16	10	1.6	Widescreen laptop displays
16:9	16	9	1.778	HD/4K video, modern TVs and monitors
1.85:1	1.85	1	1.85	Widescreen cinema
17:9	17	9	1.889	Digital cinema (DCI)
2:1	2	1	2	Univisium / modern streaming films
21:9	21	9	2.333	Ultrawide monitors
2.35:1	2.35	1	2.35	Anamorphic widescreen cinema
2.39:1	2.39	1	2.39	Modern anamorphic cinema
32:9	32	9	3.556	Super-ultrawide monitors

Frequently Asked Questions

Q: What exactly does aspect ratio measure?

It's the proportion between a rectangle's width and its height, written as W:H. A 16:9 screen is 16 units wide for every 9 units tall — the ratio describes shape, not size.

Q: How do I calculate aspect ratio from pixel dimensions?

Divide width by height to get a decimal ratio (e.g. 1920 / 1080 = 1.78, so 1.78:1). To get whole numbers instead, divide both width and height by their greatest common factor — 1920 and 1080 share a GCF of 120, giving 16:9.

Q: Can I find a missing width or height if I already know the ratio?

Yes. Switch this calculator to "Find Width" or "Find Height", enter the ratio and the dimension you do know, and it solves for the missing one while keeping the same proportions.

Q: Why does aspect ratio matter when resizing images or video?

Changing width without adjusting height by the same proportion stretches or squashes the image. Keeping the aspect ratio fixed while resizing avoids distortion and unwanted cropping.

Q: Do I need to enter units like pixels or inches?

No — aspect ratio is unitless, since it's just a proportion. A unit label is only useful for the diagonal measurement or to help you remember what the numbers represent.

Q: What is the most common aspect ratio for video today?

16:9 (decimal 1.78:1) is the standard for HD and 4K video, modern TVs, monitors, and platforms like YouTube. Vertical 9:16 has become the default for TikTok, Reels, and Shorts.