Aspect Ratio Calculator: Pixels, Video Formats and Print Sizes in 2026
This aspect ratio calculator turns any width and height in pixels into a clean ratio, or fills in the missing side when you know the ratio you need. Below it sits a field guide to the shapes that matter in 2026, from 16:9 video and vertical 9:16 clips to square posts, cinema and print.
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How the aspect ratio calculator works
An aspect ratio is the relationship between a frame’s width and its height, written as two numbers with a colon. The aspect ratio calculator above does two jobs. Enter a width and height in pixels and it reduces them to the simplest ratio. Enter a ratio plus one side and it returns the other side, rounded to whole pixels.
The reduction step uses the greatest common divisor, the largest number that divides both sides evenly. For 1920 by 1080 that number is 120, which leaves 16 and 9. For 1080 by 1350 it is 270, which leaves 4 and 5. Some sizes never reduce neatly, so the tool also shows the decimal, width divided by height.
Filling in a missing side is plain cross-multiplication. New height equals width times the second number, divided by the first. A 1080 pixel wide post at 4:5 therefore needs 1350 pixels of height, while a 1920 pixel wide frame at 16:9 needs 1080. That arithmetic is everything a resize dialog does behind its padlock icon.
Pixels, resolution and the shape of a frame
Pixels describe how much detail a frame holds; the ratio describes its shape. The two move independently. A 1280 by 720 clip and a 3840 by 2160 clip are both 16:9, yet the second carries nine times as many pixels. Scale between them and nothing is cropped. Change the ratio and something always gets cut or padded.
That difference explains a common complaint. Someone posts a sharp 4K video to a vertical feed and finds the sides missing. Resolution was never the problem. The platform simply wanted a different shape, so it cropped the centre. Checking the ratio in pixels before export saves a reshoot, and the aspect ratio calculator does it in a second.
Video ratios in 2026: 16:9 and vertical 9:16
Sixteen by nine is still the default for horizontal video. YouTube’s help centre calls it the standard ratio for the player on a computer and lists encodings such as 1920 by 1080 and 3840 by 2160. Broadcast television, laptops and most cameras share it, which makes it the safe master format for any long video project.
The shape has an engineering backstory. In the 1980s, while the industry argued over high definition, SMPTE engineer Kerns Powers proposed 16:9 as a compromise that could hold both old 4:3 television and wider cinema frames with modest bars. It worked well enough that nobody since has seriously tried to replace it for the living room screen.
Vertical 9:16 is the same rectangle on its side, the native shape for short video in 2026. TikTok’s ad specifications list vertical 9:16 as the recommended format, with horizontal and square accepted. Shorts, Reels and Stories all fill an upright phone, so 1080 by 1920 pixels is the usual working size.
Shooting once for both shapes takes planning. A common approach is to frame a 16:9 shot with the subject near the centre, leaving a vertical slice that survives the crop to 9:16. Titles and captions go inside that slice. A clip composed only for the wide frame rarely crops well into a vertical video.
Square and 4:5 for feed images
Instagram launched in 2010 with square photos only, and the 1:1 frame became shorthand for the app until portrait and landscape uploads arrived in August 2015. Square still works for carousels, product shots and anything that has to sit in a uniform grid. Album covers trained designers in that shape long before phones did.
As of 2026, Meta’s Instagram feed guide recommends 4:5 at 1440 by 1800 pixels, a taller frame that fills more of a scrolling screen. Since January 2025 the profile grid has shown posts as 3:4 previews rather than squares. A 4:5 image loses a thin strip at each side there.
Cinema, 21:9 and the ultrawide monitor
Cinema runs wider than television. Digital projection in cinemas uses two main frames: flat, at 1.85:1, and scope, at 2.39:1. The wider one is the look of most blockbusters, with black bars above and below when it appears on a 16:9 screen at home. Directors pick between them for mood as much as for scenery.
The label 21:9 comes from monitor marketing rather than film. A 2560 by 1080 panel reduces to 64:27, about 2.37:1, and a 3440 by 1440 panel reduces to 43:18, about 2.39:1. Run either through the aspect ratio calculator and the neat 21:9 disappears, but the screens do play scope films with almost no bars.
4:3 and 3:2, the older photographic shapes
Before widescreen, 4:3 was television. Standard-definition broadcast, early computer monitors at 640 by 480 and the first iPad’s 1024 by 768 screen all used it. The ratio survives in Micro Four Thirds cameras and many phone camera modes, which is why a phone photo often looks slightly squarer than the screen showing it.
Three by two comes from 35 mm film, whose frame measured 36 by 24 millimetres. Most digital camera sensors kept that shape, as did the 4 by 6 inch print. A detour: tire sizes also use an aspect ratio. In 225/65R17, the 65 is sidewall height as a percentage of tread width, and has nothing to do with pixels.
Print sizes and pixels per inch
Print adds a step, because paper is measured in inches or millimetres and images in pixels. The bridge is resolution in pixels per inch. At 300 ppi, the usual target for sharp offset printing, a 4 by 6 inch print needs 1200 by 1800 pixels and a letter-size page needs 2550 by 3300.
International paper follows ISO 216, where every A size has the ratio 1 to the square root of 2, about 1:1.414. Fold A4 in half and you get A5 in the same shape. North American letter paper, at 8.5 by 11 inches, reduces to 17:22, which is why a design made for one never fits the other cleanly.
Aspect ratio calculator presets and where they go
| Ratio | Typical pixels | Main use in 2026 |
|---|---|---|
| 16:9 | 1920 × 1080 | YouTube, television, laptops |
| 9:16 | 1080 × 1920 | TikTok, Shorts, Reels, Stories |
| 4:5 | 1440 × 1800 | Instagram feed images |
| 1:1 | 1080 × 1080 | Carousels, product grids, album art |
| 21:9 | 2560 × 1080 | Ultrawide monitors, scope-style video |
| 4:3 | 1024 × 768 | Older screens, tablets, many phone photos |
| 3:2 | 1800 × 1200 | Camera sensors, 4 by 6 inch prints |
Layout uses the same thinking: the guide to grid layout design treats columns as ratios too, and the golden ratio calculator covers the one proportion with a reputation larger than its record. For text, the type scale calculator sets sizes that suit a video caption and a poster alike, whatever their shape.
On the web, the CSS aspect-ratio property, supported in major browsers since 2021, lets a box keep its shape while its width changes. Write aspect-ratio: 16 / 9 on a video container and the height follows automatically. It is the same sum as the aspect ratio calculator, redone each time the window is resized.
Questions about the aspect ratio calculator
How is aspect ratio calculated?
Divide the width and the height by their greatest common divisor. For 1920 by 1080 pixels the divisor is 120, which leaves 16 and 9, so the ratio is 16:9. When the numbers do not reduce neatly, designers often quote the decimal instead, such as 2.39:1 for widescreen cinema, by dividing the width by the height.
What aspect ratio is 1920 x 1080?
It is 16:9, the standard shape of high definition television, most laptop screens and the YouTube player on a computer. The same ratio covers 1280 by 720, 2560 by 1440 and 3840 by 2160, which is 4K UHD. Only the pixel count changes between them, so footage scales up or down without cropping the frame.
What is the best aspect ratio for Instagram posts in 2026?
For feed images, Meta's own ad guide recommends 4:5 at 1440 by 1800 pixels as of 2026, because a taller post fills more of a phone screen. Since January 2025 the profile grid shows posts as 3:4 previews, so keep faces and text away from the top and bottom edges. Reels and Stories use vertical 9:16.
How do I calculate height from width and aspect ratio?
Multiply the width by the height part of the ratio, then divide by the width part. A 1080 pixel wide image at 4:5 needs 1080 times 5 divided by 4, which gives 1350 pixels. The same sum works backwards, so a 1920 pixel tall vertical video at 9:16 must be 1080 pixels wide.
Is 21:9 the same as 2.39:1 cinema?
Not exactly. Monitors sold as 21:9 usually run at 2560 by 1080, which is 64:27 or about 2.37:1, or at 3440 by 1440, which is 43:18 or about 2.39:1. Cinema scope projection is 2.39:1. The label 21:9 is a rounded marketing name that sits close to both, and either screen plays scope films with almost no bars.
What aspect ratio is a 4x6 photo print?
A 4 by 6 inch print is 2:3, the same shape as a 35 mm film frame and most camera sensors, which is why phone and camera photos usually print on it without heavy cropping. At 300 pixels per inch, a sharp 4 by 6 print needs an image of about 1200 by 1800 pixels.