Is this aspect ratio calculator free?

Yes. The aspect ratio calculator is free to use with no sign-up and no limits.

How do I calculate aspect ratio from a resolution?

Divide the width and height by their greatest common divisor. 1920×1080 becomes 16:9 because both numbers divide by 120. The tool does this instantly and also shows the decimal value.

Is 1366×768 really 16:9?

Not exactly. It is 683:384, about 0.05% wider than 16:9. For most screens that difference does not matter, but it can leave a thin line of bars when you fit a true 16:9 video.

Why should video sizes be even numbers?

Common video formats such as H.264 store color at half resolution, so encoders need an even width and height. A size like 1000×563 can fail to export, while 1000×562 works.

How do I convert 16:9 to 9:16?

Crop a vertical slice from the middle, for example 608×1080 from a 1920×1080 frame, or pad the frame with bars to 1920×3414. The Convert tab shows both, with the exact pixels.

What aspect ratio should I use for TikTok, Reels and Shorts?

Vertical 9:16, usually 1080×1920. YouTube Shorts also accepts square video, and Instagram allows Reels from 1.91:1 to 9:16.

Can I use it as an image aspect ratio calculator?

Yes. Drop a photo or screenshot and the image size is read on your device. Videos work the same way, so it doubles as a video aspect ratio calculator, and nothing is uploaded.

What is the difference between 21:9 and 64:27?

21:9 is a marketing name for ultrawide screens. Real panels are 64:27 (2560×1080) or 43:18 (3440×1440), both slightly wider than 21:9.

Free tool, works in your browser

Aspect Ratio Calculator

Get the size right the first time. This aspect ratio calculator shows the exact ratio of any image or video, solves the missing width or height with video-safe even numbers, and tells you exactly what to crop or pad when you move a clip from 16:9 to 9:16.

WidthHeight

Drop an image or video

Aspect ratio

16:9

As a decimal: 1.778:1

Exactly 16:9 · Widescreen (HD, 4K)

1920 × 1080

Common 16:9 resolutions

Files are read on your device and never uploaded.

Create in 16:9 with AI

Image to Video16:9 Text to Video16:9 Text to Image16:9

Exact and honestShows 683:384 and says it is about 16:9, with the difference.
Video-safe sizesRounds to even numbers that encoders accept.
Crop or padBoth results for any ratio change, in pixels.
Official platform sizesEvery preset links to its official source: a help center, an ITU recommendation or a cinema spec.

Calculate aspect ratio in 3 steps

Type a size, paste one like 1920x1080, or drop a file. Nothing is uploaded.

Width1366Height768 Drop an image or video683:384≈ 16:9 · 0.05% off
1
Enter or drop your size
Type the width and height, paste a size, or drop an image or video. The aspect ratio calculator reads it on your device and shows the exact ratio at once.
Find ratioResizeConvertPlatforms16:99:161:14:54:3Crop (keep the middle)608×1080Pad (keep everything)1920×3414
2
Pick what you need
Resize to a new width or height, change the ratio with crop or pad, or start from an official platform size for YouTube, Instagram, TikTok and more.
Copy size Copy CSSImage to Video9:16Text to Video9:16
3
Copy it or create with it
Copy the size, the CSS or an FFmpeg filter, or open our video and image generators already set to the closest ratio.

Why this aspect ratio calculator gets it right

Made for video creators first: every number is exact, every rounding is explained, and every platform size has a source.

Exact ratios, with the truth about "16:9"

Many screens are only close to a standard. A 1366×768 laptop is 683:384, about 0.05% off 16:9, and a 2560×1080 monitor is 64:27, not the 21:9 printed on the box. The aspect ratio calculator shows the exact reduced ratio, the decimal and the closest standard with the difference, so you never mistake an approximation for the real thing.

Size	Exact ratio	Closest standard
1920×1080	16:9	16:9 exact
1366×768	683:384	≈ 16:9 · 0.05% off
2560×1080	64:27	64:27 exactsold as 21:9
1001×999	1001:999	≈ 1:1 · 0.2% off

Even numbers for video, explained

Resize 16:9 to 1000 px wide and the exact height is 562.5. Most H.264 encoders (x264 with 4:2:0 color) refuse odd sizes, so the calculator rounds to 562 by default, says why, and lists nearby sizes that keep 16:9 exactly and stay even. Prefer plain rounding or multiples of 16? Switch with one tap.

16:9 at 1000 px wide

Exact height562.5

Nearest563odd: most H.264 encoders refuse it

Even (video)562

Sizes that stay exactly 16:9 and even

960×540992×5581024×5761056×594

Crop or pad, both answers at once

Changing a 1920×1080 frame to 4:3 can mean cutting 240 px from each side or adding 180 px of bars above and below. You get both results side by side, with the pixels removed or added on each edge and a preview, plus a ready FFmpeg filter.

Crop to 4:3 · 1440×1080

Aspect ratio calculator example: the same rainy street scene in 16:9

240 px + 240 px cut

Pad to 4:3 · 1920×1440

180 px + 180 px added

Platform sizes from the platforms themselves

Presets come from official help centers and specs, checked in October 2026, and say whether a number is a recommendation, a limit or only a minimum. For example, YouTube now recommends 3840×2160 thumbnails, and Instagram keeps photos up to 3:4, not just 4:5.

Platform	Official	Often quoted
YouTube thumbnail	3840×2160 (16:9)	1280×720
Instagram tallest photo	1080×1440 (3:4)	1080×1350
TikTok vertical video	minimums only	1080×1920

Cinema ratios done properly

Flat 1.85:1, the DCI container at about 1.90:1 and Scope 2.39:1 are built in, with their real pixel sizes. The 2K Scope frame of 2048×858 works out to 2.387:1, and the calculator tells you so instead of rounding it away.

Same height, different widths

16:91.778:1

1.85:11.85:1

1.90:11.896:1

64:272.37:1

2.39:12.387:1

From ratio to finished video

Found the right shape? Open Image to Video, Text to Video or Text to Image with the closest ratio already selected, and create a clip or picture that fits your platform from the first frame.

Aspect ratio calculator example: the same rainy street scene in 9:16

Create in this ratio · 9:16Image to Video9:16Text to Video9:16Text to Image9:16

One scene, four aspect ratios

The same prompt created with our text to image generator in four ratios. See how the frame changes what fits: wide shots tell the place, tall shots follow the rider.

16:91280×720
9:16720×1280
1:11024×1024
4:31152×864

Guide: how to calculate aspect ratio for images and video

The math, the standards and the habits that keep your pictures sharp and your videos accepted everywhere.

What is an aspect ratio?

An aspect ratio is the relationship between the width and the height of a picture, written as width:height. A 1920×1080 video and a 1280×720 video are both 16:9: different sizes, same shape.

An aspect ratio calculator divides both numbers by their greatest common divisor to find that shape. 1920 and 1080 share 120, which leaves 16:9. When a size is not a clean standard, the result shows its true ratio and the nearest common one.

1:1

4:5

3:4

4:3

3:2

16:9

9:16

21:9

How to calculate aspect ratio and missing sizes

To calculate aspect ratio from a size, divide width and height by their greatest common divisor. To find a missing side, multiply: new height equals new width times ratio height divided by ratio width.

Example: a 16:9 video at 1280 px wide is 1280 × 9 ÷ 16 = 720 px tall. When the result has a decimal, round to an even number for video and to the nearest pixel for images.

1920 ÷ 120 = 16 · 1080 ÷ 120 = 9 → 16:9

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

1280 × (9 ÷ 16) = 720

Turning 16:9 video into 9:16: crop or pad?

A 1920×1080 clip becomes vertical in two ways. Crop keeps the full height and cuts a 608 px wide slice from the middle, so the subject fills the phone screen. Pad keeps the whole picture and adds bars, which keeps every detail but leaves most of the screen empty.

Crop works when the action stays in the center. Pad suits slides and wide landscapes. For new AI videos, the cleanest option is to create the clip in 9:16 from the start.

16:9 frame · 1920×1080

9:16 crop · 608×1080

9:16 with bars · 1920×3414

Common resolutions for each aspect ratio

Most video uses 16:9: 1280×720, 1920×1080, 2560×1440 and 3840×2160. Some widely used sizes are only close; 854×480 is a hair wider than 16:9. Choose sizes from the list in the tool when you need an exact ratio and even numbers.

A few formats use pixels that are not square. HDV records 1440×1080 and DVD video stores 720×480, yet the player stretches each pixel so the picture shows as 16:9 or 4:3. This aspect ratio calculator assumes square pixels, the norm for phones, cameras, web video and AI generators, so enter the size the picture is shown at, such as 1920×1080, not the stored size.

Resolution	Name	Ratio
640×360	nHD (360p)	16:9
854×480	480p (FWVGA)	≈ 427:240
1280×720	HD (720p)	16:9
1920×1080	Full HD (1080p)	16:9
2560×1440	QHD (1440p)	16:9
3840×2160	4K UHD	16:9
7680×4320	8K UHD	16:9

Official sizes for YouTube, Instagram, TikTok and more

Platforms publish different kinds of numbers. YouTube recommends 16:9 for videos and 3840×2160 for thumbnails. Instagram keeps photos between 1.91:1 and 3:4 at 1080 px wide. TikTok publishes only minimum sizes, and 1080×1920 is the usual full HD vertical choice.

The calculator labels each preset as a recommendation, a limit or a minimum and links to the source, so you can check the latest wording yourself.

Platform	Size	Status	Source
YouTube Video	1920×1080	Official recommendation	support.google.com
YouTube Shorts	1080×1920	Official limit	support.google.com
YouTube Video thumbnail	3840×2160	Official recommendation	support.google.com
YouTube Shorts thumbnail	2160×3840	Official recommendation	support.google.com
Instagram Feed photo, tallest	1080×1440	Official limit	help.instagram.com
Instagram Feed photo, square	1080×1080	Within the official range	help.instagram.com
Instagram Feed photo, widest	1080×566	Official limit	help.instagram.com
Instagram Reels	1080×1920	Official minimum only	help.instagram.com
Instagram Reels ad	1440×2560	Official recommendation	facebook.com
Instagram Feed image ad	1440×1800	Official recommendation	facebook.com
TikTok Vertical video	1080×1920	Official minimum only	ads.tiktok.com
X Video	1280×720	Official recommendation	docs.x.com
LinkedIn Video ad	1920×1080	Official limit	business.linkedin.com
Pinterest Standard pin	1000×1500	Official recommendation	help.pinterest.com
Pinterest Video pin	1080×1920	Official recommendation	help.pinterest.com

Tips for perfect frames

Decide the final ratio before you shoot or generate, because cropping later always loses picture. Keep faces and text away from the edges of vertical video, where apps place their buttons. Export at the exact size of your target and avoid letting a platform stretch or squeeze your file.

Use even numbers for video sizes.
Keep the same ratio for every clip in one edit.
Check the source size before you upscale.
Save a master in the widest ratio you need, then crop copies.

What creators use an aspect ratio calculator for

From short videos to web layouts, the right shape saves time and quality.

9:16
1:1
16:9
One clip, many platforms
Plan vertical and widescreen versions of the same video before you export.
3840×2160
Rain ride
Thumbnails and covers
Hit the recommended thumbnail size without stretching your artwork.

/* keeps a 16:9 box at any width */
.video {
  width: 100%;
  aspect-ratio: 16 / 9;
}

Responsive web design

Copy the CSS aspect-ratio value for video embeds and image boxes.

Create in this ratio
AI video and images
Create in 16:9, 9:16, 1:1 or 21:9 from the start instead of cropping afterwards.
2.39:1
Ultrawide and cinema
Work out letterbox bars for 2.39:1 footage or 64:27 monitors.
4:3 → 4:5
Photo posts and editing
Turn a 4:3 phone photo into a 4:5 post without guessing the crop.