Aspect Ratio Calculator for Video and Images
Type a width and height to get the simplified ratio. Lock a ratio like 16:9 or 9:16, change one side, and the other is worked out for you. Common sizes for YouTube, Shorts, Reels and TikTok are one tap away.
Common sizes
| Pixels | 2,073,600 |
|---|---|
| Megapixels | 2.07 |
| Flipped | 1080×1920 (9:16) |
Works in your browser. Nothing is uploaded.
How to use the aspect ratio calculator
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Find the ratio of a size
Untick "Lock ratio", then type a width and height. The calculator reduces them to the smallest whole numbers (1920×1080 becomes 16:9) and shows the decimal form and orientation.
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Solve a missing side
Leave the lock on, pick a ratio such as 16:9, and type the width you need. The height fills in. Type a height instead and the width follows.
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Use a custom ratio
Type any ratio into the two ratio boxes, including decimals like 2.39 : 1 for widescreen film. Tap a preset chip to jump back to a common one.
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Check the preview
The box on the right redraws to the shape you entered, so you can see at a glance whether a size is tall, wide or square before you export.
How to calculate an aspect ratio by hand
An aspect ratio is width divided by height, written as two whole numbers. To simplify a size, find the greatest common divisor (GCD) of the width and height and divide both by it. For 1920×1080 the GCD is 120: 1920 ÷ 120 = 16 and 1080 ÷ 120 = 9, so the ratio is 16:9.
To find a missing side, use height = width × (ratio height ÷ ratio width). A 16:9 video 1280 pixels wide is 1280 × 9 ÷ 16 = 720 pixels tall. For the width, flip it: width = height × (ratio width ÷ ratio height). A 9:16 video 1920 tall is 1920 × 9 ÷ 16 = 1080 wide.
Some sizes do not reduce neatly. A 1366×768 laptop screen simplifies to 683:384, but it is sold as 16:9 because it is within a fraction of a percent. The calculator tells you when a size is "close to" a common ratio. "21:9" is a looser name still: 2560×1080 and 3440×1440 are both sold as 21:9 even though their exact ratios are 64:27 and 43:18.
Common aspect ratios and pixel sizes
Most of these sizes are one tap away in the calculator above.
| Ratio | Shape | Common pixel sizes | Used for |
|---|---|---|---|
| 16:9 | Wide | 3840×2160, 2560×1440, 1920×1080, 1280×720 | YouTube videos, TV, most monitors |
| 9:16 | Tall | 2160×3840, 1080×1920, 720×1280 | YouTube Shorts, Reels, TikTok, Stories |
| 1:1 | Square | 1080×1080, 720×720 | Square feed posts, profile photos |
| 4:5 | Tall | 1080×1350 | Instagram portrait feed posts |
| 4:3 | Wide | 1440×1080, 1024×768, 640×480 | Older TV, iPad screens, many photo cameras |
| 3:2 | Wide | 6000×4000, 3000×2000 | DSLR and mirrorless photos |
| 21:9 | Ultrawide | 3440×1440, 2560×1080 | Ultrawide monitors, cinematic crops |
4K UHD (3840×2160) and 1080p are both 16:9, so you can scale between them without cropping. 1080×1920 is the same shape as 1920×1080, turned on its side.
The 16:9 calculator: sizes at every width
For 16:9, height is always width × 0.5625. A few you will need often: 640×360, 854×480, 1280×720 (720p), 1600×900, 1920×1080 (1080p), 2560×1440 (1440p) and 3840×2160 (4K). Each of these is a whole number of pixels on both sides.
Not every width works out cleanly. 1000 pixels wide at 16:9 is 562.5 pixels tall, so the calculator rounds and tells you the exact value. For video, round to an even number: most encoders store color at half resolution, so odd sizes can be rejected or padded.
Need it the other way up? 9:16 is the same table with the numbers swapped: 720×1280, 1080×1920, 2160×3840.
Getting the ratio right for each platform
The right shape depends on where the video will play. Our size guides cover each platform in detail, including safe zones for captions.
- YouTube Shorts: 9:16 at 1080×1920. See the YouTube Shorts size guide.
- TikTok: 9:16 at 1080×1920. See the TikTok video size guide.
- Instagram Reels: 9:16 at 1080×1920; the profile grid shows a 3:4 crop. See the Instagram Reels size guide.
- YouTube thumbnails: 16:9 at 1280×720. See the YouTube thumbnail size guide.
- Long YouTube videos: 16:9, at 1920×1080 or larger.
Changing a video from 16:9 to 9:16
Same pixels, very different shape. A 1920×1080 frame has to lose most of its width to become 1080×1920. You have three options:
Crop
Cut a 9:16 slice out of the 16:9 frame. A 1080-tall slice of a 1920×1080 video is only about 608 pixels wide, so it needs scaling up and the person has to stay inside it.
Letterbox
Shrink the wide frame and add bars above and below. Nothing is lost, but the video fills about a third of a phone screen.
Reframe
Follow the speaker with a moving crop so the subject stays centered. This is what Short.now does automatically when it turns long videos into Shorts.
Turn 16:9 videos into 9:16 without cropping by hand
Short.now reframes your horizontal videos to 9:16 and keeps the speaker in shot, then adds captions, so a long recording becomes Shorts, Reels and TikToks.
Questions
Divide the width and height by their greatest common divisor. 1920×1080 divided by 120 gives 16:9. The calculator does this for any size you type in.
Common 16:9 sizes are 1280×720, 1920×1080, 2560×1440 and 3840×2160. For any width, height = width × 9 ÷ 16.
The standard 9:16 size is 1080×1920 pixels, used for YouTube Shorts, Instagram Reels and TikTok. 720×1280 and 2160×3840 are also 9:16.
Yes. 1080 and 1350 share a divisor of 270, and 1080 ÷ 270 = 4, 1350 ÷ 270 = 5. It is the tall size Instagram uses for portrait feed posts.
Almost. It simplifies to 683:384, which is about 1.779:1 against 16:9’s 1.778:1. It is sold as 16:9 and displays 16:9 video with no visible bars.
4K UHD at 3840×2160 is 16:9. Cinema 4K (DCI) at 4096×2160 is wider, about 1.9:1.
