To find your aspect ratio, divide the width by the height and reduce the two numbers by their greatest common divisor: 1920x1080 reduces to 16:9 (decimal 1.778), 1080x1350 reduces to 4:5 (0.8) and 1080x1920 reduces to 9:16 (0.5625). If you are asking how to know what my aspect ratio is for a screen, an image or a video, the only thing that changes is where you read the width and height.
This guide from the Playcut spec library covers all three cases on every operating system, with a lookup table at the end.
What an aspect ratio is (and why it is not resolution)
An aspect ratio is the width of an image, video or screen divided by its height, written as two whole numbers with a colon (16:9) or as one decimal (1.78). It says nothing about how many pixels there are, only their proportion. MDN's CSS aspect-ratio reference defines it the same way: a width number, a slash, and a height number.
Ratio versus resolution
Resolution is the pixel count; ratio is the shape. 1280x720, 1920x1080, 2560x1440 and 3840x2160 are four resolutions that all reduce to 16:9, so a 16:9 video fills any of those screens without bars. Double both numbers and the ratio does not move.
Display aspect ratio versus pixel aspect ratio
Video files carry two ratios. The sample (pixel) aspect ratio describes the shape of one pixel, which is 1:1 for almost everything shot or generated today. The display aspect ratio is the shape of the whole frame, and it is the one you care about. That is why ffprobe prints both, and why a 1080x1350 file reports 1:1 and 4:5 at the same time.
How to know what my aspect ratio is: divide width by height and reduce
To find any aspect ratio, divide both the width and the height by their greatest common divisor. 1080 and 1350 share a factor of 270, so 1080x1350 reduces to 4:5, and 1080 divided by 1350 gives the decimal 0.8. The whole method is three steps.
Step 1: find the pixel width and height
Read the two numbers from the file's info panel, the video's stream data or the display's native resolution. The per-device instructions below show exactly where each one lives. Always use pixels, never the physical size in inches or centimetres, unless you are measuring paper.
Step 2: divide both numbers by their greatest common divisor
Find the largest whole number that divides both dimensions cleanly. 2560 and 1440 share 160, giving 16:9. 1920 and 1200 share 240, giving 8:5, which everyone writes as 16:10. If you would rather not hunt for the divisor, the free aspect ratio calculator does the reduction when you type the two pixel values.
Step 3: match the decimal to a named ratio
Divide width by height and compare the decimal with the lookup table further down. A result within about 1 percent of a named ratio is that ratio for every practical purpose; platforms crop to the nearest supported shape anyway.
Worked examples
- 1350x2250: both divide by 450, so 3:5 (0.6).
- 8.5 x 11 inches (US Letter): multiply by 10 to get 85:110, divide by 5, so 17:22 (0.773).
- 8 x 10 inches: both divide by 2, so 4:5 (0.8), the same shape as a 1080x1350 post.
- 6000x4000 (a 24-megapixel camera photo): both divide by 2000, so 3:2 (1.5).
- 4032x3024 (a 12-megapixel phone photo): both divide by 1008, so 4:3 (1.333).
When the reduced fraction is ugly
Some dimensions reduce to numbers nobody uses. 3440x1440 reduces to 43:18 (2.389) and 2560x1080 to 64:27 (2.370); both are sold as 21:9 monitors. A 1170x2532 phone screen reduces to 195:422 (0.462), which is quoted as roughly 9:19.5. In those cases give the decimal plus the marketing name, and let the exact fraction go.
How to find the aspect ratio of an image file
Every operating system shows an image's pixel dimensions in its file-info panel, and the ratio is those two numbers reduced. The panel is in a different place on each platform, so here is the exact path for each one.
On Windows
- Right-click the image file and choose Properties.
- Open the Details tab.
- Under Image, read Dimensions (for example 1080 x 1350) or the separate Width and Height lines.
On macOS
- Select the file in Finder and press Command-I; Dimensions appears under More Info.
- Or open the image in Preview, choose Tools, then Show Inspector, and read Image Size.
- In Terminal,
sips -g pixelWidth -g pixelHeight photo.pngprints both values;exiftool -ImageSize photo.jpgprints them as one line.
On iPhone and Android
- iPhone: open the photo in Photos, then swipe up or tap the info button to see the pixel dimensions and megapixel count.
- Android: open the photo in Google Photos and swipe up to the Details panel, which lists the width and height.
iPhone photos are 4:3 (or 3:4 in portrait) and iPhone video is 16:9 or 9:16, while the screen itself is 19.5:9. The iPhone aspect ratio sheet lists the exact pixel sizes per model so you can confirm the number you just read.
In a browser
- Open the image in its own tab; most browsers print the width and height in the tab title.
- Or open DevTools, select the image element and read
naturalWidthandnaturalHeightin the console.
Once you have the numbers, reduce them or type them into the calculator. If the result does not match the platform you are posting to, the free image resizer crops or pads the file to the target shape without stretching it.
How to find the aspect ratio of a video file
The fastest way to find a video's aspect ratio is ffprobe, which ships with FFmpeg and prints the display aspect ratio directly with no arithmetic. If it prints N/A, the file has no signalled pixel aspect ratio; reduce width and height yourself. On a 1080x1350 H.264 file the command below prints width=1080, height=1350 and display_aspect_ratio=4:5.
ffprobe -v error -select_streams v:0 -show_entries stream=width,height,display_aspect_ratio -of default=noprint_wrappers=1 video.mp4
The -select_streams v:0 flag limits the output to the first video stream and
-show_entries picks the three fields you need. Both flags are documented in the
official ffprobe manual.
If the file carries a non-square pixel aspect ratio, add sample_aspect_ratio to the list to
see it.
Without a terminal
- MediaInfo (free, Windows, macOS and Linux): open the file and read Width, Height and Display aspect ratio on the Video track.
- VLC: play the file, open Tools, then Codec Information, and read Resolution under Stream 0.
- QuickTime Player on macOS: open Window, then Show Movie Inspector, and read the Format line.
- Windows: right-click the file, choose Properties, open Details and read Frame width and Frame height under Video.
An animated GIF can go through the same QuickTime Player check once you turn a GIF into a .mov file.
How to find your screen or monitor aspect ratio
Your screen's aspect ratio is its native resolution reduced. Read the Recommended value in Windows Settings or the default in macOS Displays, then divide: 1920x1080 and 2560x1440 are 16:9, 1920x1200 and 2560x1600 are 16:10, and 3440x1440 is 43:18, sold as 21:9.
Your browser reports this screen as: enable JavaScript to read the live value, or follow the steps below.
Windows 10 and 11
- Open Start, then Settings, System, Display.
- Read Display resolution and use the entry marked Recommended, which is the panel's native size, as Microsoft's screen resolution guide advises.
- Reduce the two numbers; a scaled or lower setting still has the same ratio as the native one.
macOS
- Open System Settings, then General, then About; the Displays section lists the panel's native resolution, for example 3024 x 1964.
- Or open System Settings, then Displays, click Advanced and turn on Show resolutions as list to see every pixel size the panel supports, native first. (On macOS 12 and earlier, hold Option and click Scaled in System Preferences instead.)
- Reduce the numbers; a Retina panel at 2880x1800 is 16:10 whether it is scaled or not, and 3024x1964 is 1.54, quoted as roughly 3:2.
In a browser or from the spec sheet
In any browser console, screen.width / screen.height returns the decimal for
the current display. If you cannot reach the settings at all, the native resolution line on
the manufacturer's product page gives the same two numbers.
Resolution and decimal lookup table
Once you have width and height, this table maps the common resolutions to their reduced ratio, decimal and pixel count. Read down the decimal column if you calculated one and want the name that goes with it.
| Width x height | Ratio | Decimal | Megapixels | Where it is used |
|---|---|---|---|---|
| 3440 x 1440 | 43:18 | 2.389 | 4.95 | Ultrawide monitor, sold as 21:9 |
| 1280 x 720 | 16:9 | 1.778 | 0.92 | 720p HD video |
| 1920 x 1080 | 16:9 | 1.778 | 2.07 | Full HD monitors, YouTube, broadcast |
| 2560 x 1440 | 16:9 | 1.778 | 3.69 | 1440p monitors |
| 3840 x 2160 | 16:9 | 1.778 | 8.29 | 4K UHD video and TVs |
| 1920 x 1200 | 16:10 | 1.600 | 2.30 | Office monitors |
| 2560 x 1600 | 16:10 | 1.600 | 4.10 | MacBook and laptop panels |
| 6000 x 4000 | 3:2 | 1.500 | 24.00 | Full-frame and APS-C camera stills |
| 4032 x 3024 | 4:3 | 1.333 | 12.19 | Phone camera photos |
| 1280 x 1024 | 5:4 | 1.250 | 1.31 | Older office monitors |
| 1080 x 1080 | 1:1 | 1.000 | 1.17 | Square feed posts |
| 1080 x 1350 | 4:5 | 0.800 | 1.46 | Instagram portrait, 8x10 prints |
| 1080 x 1440 | 3:4 | 0.750 | 1.56 | Portrait phone photos, Instagram tall feed posts |
| 1000 x 1500 | 2:3 | 0.667 | 1.50 | Pinterest Pins, 4x6 prints |
| 1350 x 2250 | 3:5 | 0.600 | 3.04 | Tall poster exports |
| 1080 x 1920 | 9:16 | 0.563 | 2.07 | Reels, Shorts, TikTok, Stories |
How close is close enough
Treat anything within 1 percent of a named ratio as that ratio. 0.8 and 0.81 are both 4:5 in practice, and 1.77 is 16:9. Beyond that the gap becomes visible as a crop or a bar: 16:10 is 10 percent narrower than 16:9, 3:2 is 15.6 percent narrower, and 4:3 is 25 percent narrower, so none of the three passes as widescreen.
What to do with the ratio once you know it
Knowing the ratio tells you whether a file uploads untouched or gets cropped. The standard HD frame is 1920 x 1080 at 16:9, defined in SMPTE ST 274, the 1920 x 1080 image sample structure standard, and it is the shape YouTube's default player and broadcast television are built around.
Pinterest recommends 2:3 for standard Pins in its product specs. Instagram currently displays feed posts between 1.91:1 landscape and 3:4 portrait uncropped, and Meta's Instagram feed image specs recommend 4:5 at 1440 x 1800 pixels; anything taller than 3:4 is cropped.
| Placement | Ratio | Typical pixels | If your file is a different ratio |
|---|---|---|---|
| YouTube standard player | 16:9 | 1920 x 1080 | Padded with bars by the player |
| YouTube Shorts, Reels, TikTok | 9:16 | 1080 x 1920 | Cropped or letterboxed to vertical |
| Instagram feed, portrait | 4:5 | 1080 x 1350 | Files taller than 3:4 are cropped; 4:5 and 3:4 both display uncropped |
| Instagram feed, tall portrait | 3:4 | 1080 x 1440 | Tallest uncropped feed shape; 9:16 files lose the top and bottom |
| Instagram feed, landscape | 1.91:1 | 1080 x 566 | Wider files are cropped to 1.91:1 |
| Pinterest standard Pin | 2:3 | 1000 x 1500 | Very tall Pins are cut off in feed |
| Pinterest full-screen video Pin / Idea ad | 9:16 | 1080 x 1920 | Cropped to vertical |
| Square feed post | 1:1 | 1080 x 1080 | Cropped to the centre square |
| 8x10 print | 4:5 | 2400 x 3000 at 300 dpi | Edges trimmed by the lab |
Which AI models output your ratio
Generation is the one place where the ratio is free to choose, so pick it before you spend credits. In Playcut, Veo 3.1 renders 16:9 and 9:16 only, Seedance 2.0 adds 21:9, 4:3, 1:1 and 3:4, and Grok Imagine's video model adds 3:2 and 2:3. For stills, Nano Banana Pro covers ten ratios including 4:5, 5:4 and 21:9, while Grok Imagine's image model adds 2:1 and 1:2.
That means a 4:5 image is a native render, but 4:5 video comes from one model only: HappyHorse 1.1 renders it natively, while Veo, Seedance, Grok and Wan do not. On Seedance, Wan or Grok Imagine Video, generate at 3:4 or 1:1 in Playcut's video generator (Veo 3.1 has only 9:16 to crop from), then trim to 4:5 with the safe zone checker open so the subject stays clear of platform overlays.
The 4:5 aspect ratio sheet lists every 4:5 pixel size, and the 3:2 and 2:3 aspect ratio sheet covers the camera-native shape most photo libraries arrive in.
If the file came out of Midjourney, its ratio was set by the --ar parameter; the
Midjourney aspect ratio guide maps each value to the pixel size
the model returns.
Resizing without stretching
Never scale one axis on its own; faces and type distort immediately. Crop when the subject is central and you can afford to lose edges, pad when every pixel matters and bars are acceptable, and regenerate when the file came out of an AI model in the first place. A regenerated frame at the target ratio composes for that shape instead of losing a third of the picture to a crop.