Aspect Ratio Calculator
Find a ratio like 16:9, resize without changing shape, and check screen sharpness.
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1920 × 1080 is exactly 16:9.
HD video and almost every television and monitor.
Resize keeping 16:9
height = 720 px
width = 1280 px
Results are rounded to whole pixels, so the shape can be off by a hair — occasionally enough to leave a one-pixel gap.
16:9 at common widths
| Width | Height |
|---|---|
| 640 px | 360 px |
| 1280 px | 720 px |
| 1920 px | 1080 px |
| 2560 px | 1440 px |
| 3840 px | 2160 px |
Pixel density
Screens are advertised by their diagonal, so the pixel diagonal has to be reconstructed before it can be divided by it.
About 90–110 is a normal desktop monitor. From 140 up, you can’t see individual pixels. Phones go over 400 because you hold them close.
Your files stay on your device
How to use it
Enter a width and height to get the aspect ratio, like 16:9, plus the closest standard ratio. Then resize while keeping the same shape.
An aspect ratio is a screen or image’s shape — like 16:9 for most TVs and videos, or 9:16 for phone videos. Enter a width and height and you get the ratio straight away.
Some sizes don’t come out neatly. A 1366×768 laptop screen is almost 16:9 but not quite, so you’ll see the exact ratio, the nearest standard one, and how far apart they are.
Need a new size with the same shape? Type a new width or height in the resize panel and the other number is filled in for you.
Wondering how sharp a screen is? Enter its size in inches to get its pixels per inch (PPI). Around 100 is normal for a desktop monitor; 140 and up looks crisp.
Common resolutions and their ratios
Most screens and videos use one of a handful of shapes. The odd ones out are usually older screens that were aiming for 16:9.
| Resolution | Aspect ratio |
|---|---|
| 1280 × 720 (720p) | 16:9 |
| 1920 × 1080 (1080p) | 16:9 |
| 2560 × 1440 (1440p) | 16:9 |
| 3840 × 2160 (4K UHD) | 16:9 |
| 4096 × 2160 (DCI 4K) | 256:135 (≈1.90:1) |
| 1366 × 768 | 683:384 (≈16:9) |
| 1920 × 1200 | 16:10 |
| 3440 × 1440 | 43:18 (≈21:9) |
| 1280 × 1024 | 5:4 |
| 1080 × 1920 (vertical video) | 9:16 |
16:9 dimensions at common widths
The height that goes with each width at 16:9. Widths that divide by 16 give a whole number, which is why standard sizes use them.
| Width | Height at 16:9 |
|---|---|
| 640 px | 360 px |
| 1280 px | 720 px |
| 1600 px | 900 px |
| 1920 px | 1080 px |
| 2560 px | 1440 px |
| 3840 px | 2160 px |
| 7680 px | 4320 px |
Pixel density of common screens
Sharpness depends on both the pixels and the screen size. That’s why a 32-inch 4K monitor looks less sharp than a 27-inch 4K one.
| Screen | Pixel density |
|---|---|
| 24" 1920 × 1080 | 91.8 ppi |
| 27" 1920 × 1080 | 81.6 ppi |
| 27" 2560 × 1440 | 108.8 ppi |
| 32" 3840 × 2160 | 137.7 ppi |
| 27" 3840 × 2160 | 163.2 ppi |
| 13.3" 2560 × 1600 | 226.9 ppi |
FAQ
What is the aspect ratio of 1920 × 1080?
Exactly 16:9.
Is 1366 × 768 a 16:9 resolution?
Almost, but not exactly. It’s close enough to be sold as 16:9, but 16:9 videos may show a one-pixel bar.
How do I work out an aspect ratio?
Divide the width and height by the biggest number that goes into both. For 2560 × 1440 that’s 160, giving 16:9. The calculator does it for you.
What resolution is 21:9?
“21:9” is a marketing name. A 3440 × 1440 ultrawide is really 43:18, and 2560 × 1080 is 64:27.
What’s a good pixel density for a monitor?
About 90–110 PPI is normal at desk distance. Above about 140, you can’t see individual pixels. Phones go over 400 because you hold them close.
Is PPI the same as DPI?
Not quite. PPI is pixels on a screen; DPI is ink dots on paper. Apps often use them interchangeably.
How it worksFor the curious
The ratio is the width and height divided by their greatest common divisor: 1920×1080 has a GCD of 120, giving 16:9.
1366×768 reduces to 683:384 — exact, but not a named ratio. At 1.7786 against 16:9’s 1.7778 the difference is 0.05%, enough to leave a one-pixel bar on full-screen 16:9 content. So the exact reduction, the nearest named ratio, and the error are all shown.
Resized dimensions are rounded to whole pixels, which can shift the true ratio very slightly when it does not divide evenly.
Pixel density reconstructs the pixel diagonal with Pythagoras and divides by the advertised diagonal: a 27-inch 2560×1440 monitor is 108.8 ppi. PPI counts screen pixels; DPI counts printed ink dots — related, but not the same thing.