Quick lookup
Common resolutions for each aspect ratio
Quick reference for the standard pixel dimensions at popular aspect ratios. All rows preserve the same shape - only the size changes.
| Aspect ratio | Low | Standard | High | Used for |
|---|---|---|---|---|
| 16:9 | 1280×720 | 1920×1080 | 3840×2160 | YouTube, TV, monitors |
| 9:16 | 720×1280 | 1080×1920 | 2160×3840 | TikTok, Reels, Stories |
| 4:3 | 1024×768 | 1600×1200 | 2048×1536 | iPad, old monitors |
| 1:1 | 720×720 | 1080×1080 | 2048×2048 | Instagram post, avatars |
| 3:2 | 1080×720 | 1620×1080 | 3000×2000 | DSLR photos, prints |
| 21:9 | 2560×1080 | 3440×1440 | 5120×2160 | Ultrawide, cinema |
| 4:5 | 864×1080 | 1080×1350 | 1728×2160 | Instagram portrait |
To keep an image sharp, export at the highest resolution your platform accepts, then let it downscale. Upscaling a small image always looks soft.
The basics
What is an aspect ratio?
An aspect ratio is the proportional relationship between width and height, written as W:H. A 16:9 ratio means that for every 16 units of width there are 9 of height. It describes shape independent of size - 1280×720, 1920×1080, and 3840×2160 are all 16:9. This calculator solves the missing dimension for any ratio, or works out the simplified ratio from raw pixel dimensions.
How it's calculated
The math
Finding the missing dimension
Given a ratio W:H and one dimension, scale to find the other:
- Height from width: height = width × H / W. For 1920 wide at 16:9 → 1920 × 9 / 16 = 1080
- Width from height: width = height × W / H. For 1080 tall at 16:9 → 1080 × 16 / 9 = 1920
Finding the ratio from dimensions
Divide both numbers by their greatest common divisor (GCD). 1920 and 1080 share a GCD of 120, giving 16:9. 1440×900 reduces to 8:5.
Practical guide
Which ratio for which platform?
16:9 - widescreen
The default for YouTube, TV, computer monitors, and most presentations. If unsure, use this.
9:16 - vertical
TikTok, Instagram Reels, YouTube Shorts, and Stories. Shot and viewed in portrait on phones.
1:1 - square
Classic Instagram feed posts, profile pictures, album covers. Works everywhere.
4:5 - portrait feed
Instagram's tallest feed format. Takes up more vertical space than square, grabbing more attention.
4:3 - traditional
Older monitors, iPads, many digital cameras, and document scans. More square than widescreen.
21:9 - cinematic
Ultrawide monitors and a film-like look. The monitor approximation of cinema's ~2.39:1 standard.
The trade-off
Cropping between ratios
You can't change ratio without losing something
Behind the scenes
Privacy and how it runs
Runs in your browser
Common questions
What is the height for a 1920px width at 16:9?
1080 pixels. 1920 × 9 / 16 = 1080. That's why 1920×1080 ("Full HD" or "1080p") is the most common video resolution.
How do I find the aspect ratio of a photo?
Unlock the ratio, enter the photo's pixel width and height, and the calculator reduces them to the simplest whole-number ratio. A 4032×3024 phone photo is 4:3.
What ratio is 1280×1024?
5:4. It's a slightly squarer ratio used by some older LCD monitors, not quite the same as 4:3.
What's the best resolution for YouTube?
16:9 at 1920×1080 (1080p) is the practical standard; 3840×2160 (4K) for higher quality. Both are 16:9 - same shape, more pixels.
Why do my videos have black bars?
The video's aspect ratio doesn't match the screen or player. A 4:3 video on a 16:9 screen gets bars on the sides (pillarboxing); a 21:9 film on a 16:9 screen gets bars top and bottom (letterboxing). Match the ratio to avoid them.
What is 1920x1080 aspect ratio?
1920×1080 is 16:9. Divide both numbers by their greatest common divisor of 120 and you get 16:9. It is also called Full HD or 1080p, the standard for video, YouTube, and most monitors.
What is 16:9 in pixels?
16:9 is a shape, not a fixed pixel count, so it depends on the height you pick. At 720 tall it is 1280×720, at 1080 tall it is 1920×1080, and at 1440 tall it is 2560×1440. Multiply the height by 16 and divide by 9 to get the width.
What aspect ratio is 1024x1024?
1:1, a perfect square. Any image with equal width and height reduces to 1:1, which is why 1024×1024, 512×512, and 2048×2048 are all square. It is a common default for AI image generators and profile pictures.
How do I convert 4:3 to 16:9?
Either crop or add bars. To crop, keep the width and trim the height to width × 9 / 16, so a 1440-wide 4:3 frame becomes 1440×810. To keep the whole frame, place it on a 16:9 canvas and accept pillarbox bars on the left and right.
Quick lookup
Resolution to aspect ratio reference
Look up any common screen or image resolution to see the aspect ratio it reduces to. Different pixel counts that share the same shape share the same ratio.
| Resolution | Aspect ratio | Common name or use |
|---|---|---|
| 1280×720 | 16:9 | HD, 720p |
| 1920×1080 | 16:9 | Full HD, 1080p |
| 2560×1440 | 16:9 | QHD, 1440p |
| 3840×2160 | 16:9 | 4K UHD |
| 1366×768 | ~16:9 | Common laptop screen |
| 1600×900 | 16:9 | HD+ monitor |
| 1920×1200 | 16:10 | 16:10 productivity monitor |
| 2560×1080 | 21:9 | Ultrawide |
| 3440×1440 | 21:9 | Ultrawide QHD |
| 1024×768 | 4:3 | XGA, classic monitor |
| 800×600 | 4:3 | SVGA |
| 1280×1024 | 5:4 | SXGA LCD |
| 1080×1350 | 4:5 | Instagram portrait |
| 1080×1920 | 9:16 | Reels, TikTok, Stories |
| 1024×1024 | 1:1 | Square, AI image default |
Ultrawide 2560×1080 and 3440×1440 are marketed as 21:9, though the exact reductions are 64:27 and 43:18. 1366×768 is close to 16:9 but not exact, which is why some full-screen video shows thin bars on those laptop panels.
16:9, 4:3, 21:9, 1:1, 9:16
Aspect ratio in pixels
An aspect ratio has no fixed pixel size. Pick a height (or a width) and scale to fill the shape. To get the width from a height, multiply the height by the first number of the ratio and divide by the second. A 16:9 banner 1080 pixels tall works out to 1080 × 16 / 9 = 1920, so 1920×1080.
- 16:9 in pixels: 720 tall = 1280×720, 1080 tall = 1920×1080, 1440 tall = 2560×1440. Width = height × 16 / 9.
- 4:3 in pixels: 768 tall = 1024×768, 600 tall = 800×600, 1536 tall = 2048×1536. Width = height × 4 / 3.
- 21:9 in pixels: 1080 tall = 2560×1080, 1440 tall = 3440×1440. These are the marketed ultrawide sizes.
- 1:1 in pixels: width equals height, so 1080×1080, 512×512, or 1024×1024.
- 9:16 in pixels: 1280 tall = 720×1280, 1920 tall = 1080×1920. Width = height × 9 / 16. This is the vertical form of 16:9.
Crop or letterbox
Converting 4:3 to 16:9 (and back)
4:3 to 16:9
16:9 is wider than 4:3, so you either crop the top and bottom or add bars on the sides.
- Crop to fill: keep the width and trim the height. A 1440×1080 (4:3) frame cropped to 16:9 becomes 1440×810, losing 270 pixels of height.
- Fit with bars: place the full 4:3 frame on a 16:9 canvas. On a 1920×1080 canvas the image fills 1440×1080 and leaves 240-pixel pillarbox bars on each side.
16:9 to 4:3
4:3 is taller and narrower, so you either crop the sides or add bars on the top and bottom.
- Crop to fill: keep the height and trim the width. A 1920×1080 (16:9) frame cropped to 4:3 becomes 1440×1080, losing 480 pixels of width.
- Fit with bars: on a 4:3 canvas like 1440×1080 the 16:9 image fills 1440×810 and leaves 135-pixel letterbox bars top and bottom.
Decide before you shoot
GCD reduction
Pixels to aspect ratio: worked examples
To turn raw pixel dimensions into a ratio, divide both numbers by their greatest common divisor (GCD). The result is the simplest whole-number ratio. For 1920×1080 the GCD is 120: 1920 / 120 : 1080 / 120 = 16:9.
- 1600×900: GCD is 100, so 1600 / 100 : 900 / 100 = 16:9.
- 2560×1440: GCD is 160, so 2560 / 160 : 1440 / 160 = 16:9.
- 1080×1350: GCD is 270, so 1080 / 270 : 1350 / 270 = 4:5.
- 1440×900: GCD is 180, so 1440 / 180 : 900 / 180 = 8:5, usually written 16:10.
- 1366×768: GCD is only 2, giving 683:384. That does not reduce cleanly, so it is treated as approximately 16:9.
Related calculators
Design and media tools that pair with the aspect ratio calculator.
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