Aspect ratio calculator
Lock a ratio and change one dimension; the other follows. No upload, no image needed.
Locked: changing a dimension keeps this ratio.
1920 × 1080 is exactly 16:9.
Used for: YouTube video and thumbnails, HD and 4K screens.
Got the numbers? Resize an image to exactly this size, crop to the shape, or add a border to reach it without cutting anything off.
| Width | Height |
|---|---|
| 3840 | 2160 |
| 1920 | 1080 |
| 1600 | 900 |
| 1280 | 720 |
| 1080 | 608 |
| 800 | 450 |
| 640 | 360 |
| 320 | 180 |
How do I calculate an aspect ratio?
Two directions, one calculator
Most of the time the question is: I need this at 16:9 and 1200 wide, so how tall? Lock the ratio, type the width, read the height. The other dimension follows every keystroke.
Sometimes it is the other way round: what shape is this thing I already have? Unlock the ratio and type both dimensions, and the exact simplified ratio appears — along with the nearest standard shape, if it is close to one, and what that shape is normally used for.
Exact ratios, and ratios people mean
1000×667 simplifies to 1000:667, which is technically correct and tells you nothing. It is 3:2 to within a rounding error, and 3:2 is the answer you wanted — it is the shape of 35 mm film, of most camera sensors, and of a 6×4 inch print.
So the calculator reports both, labelled differently. The exact simplification is the arithmetic; the named ratio is what the number means. Where they disagree, the second one is almost always the useful one, and where nothing standard is close, it says that instead of forcing a name onto an unusual shape.
Standard ratios and what they are for
| Ratio | Where you meet it |
|---|---|
| 1:1 | Profile pictures, avatars, Instagram squares, app icons |
| 4:3 | Older cameras, tablet screens, presentation slides |
| 3:2 | 35 mm film, most DSLRs, 6×4 inch prints |
| 16:9 | YouTube video and thumbnails, HD and 4K screens |
| 21:9 | Ultrawide monitors, cinematic video |
| 9:16 | Stories, Reels, TikTok, phone wallpapers |
| 4:5 | Instagram portrait posts — the tallest feed post allowed |
| 2:3 | Portrait prints, book covers, Pinterest pins |
| 3:4 | Portrait photos from older cameras |
| 1.91:1 | Link previews on Facebook and LinkedIn |
| 5:4 | 8×10 inch prints |
| 7:5 | 7×5 inch prints |
Then there are three things you can do about it
Knowing the numbers is half of it. Once you have them:
Resize if the image is already the right shape and only the pixel count is wrong. Nothing is lost from the frame — the image resizer takes the two numbers directly.
Crop if the shape is wrong and the edges are expendable. The cropper has the standard ratios as presets, and you choose which part survives rather than letting the destination decide.
Pad if the shape is wrong and nothing is expendable. Adding bars to the short side reaches any ratio without removing a pixel, which is the right answer when the thing that would be cropped is the point of the picture — the border tool does that.
Sizes that already have a page
Six of the most-asked-for pixel sizes open the resizer with the numbers filled in and explain what that size is for: 1080 × 1080 for square posts, 1920 × 1080 for Full HD, 1280 × 720 for video thumbnails, 1200 × 630 for link previews, 1080 × 1350 for portrait feed posts, and 1080 × 1920 for stories and vertical video.
The one that catches people out
Uploading an image whose ratio does not match what a platform expects rarely produces an error. It produces a crop, decided by the platform, usually from the centre. That is how a tall photograph ends up as a square with the top of someone’s head missing, and why it is worth working out the shape in advance and choosing the crop yourself.
Common questions
- What aspect ratio is 1920×1080?
- Exactly 16:9. Dividing both numbers by 120 gives 16 and 9 with nothing left over, which is what makes it exact rather than approximate — a distinction that matters, because plenty of sizes people call 16:9 are not quite.
- How do I resize an image without distorting it?
- Change one dimension and let the other follow the ratio. Lock the ratio here, type your required width, and the height that keeps the shape appears. Typing both numbers independently is what stretches an image — the picture is forced into a frame that is not its shape, and everything in it gets subtly taller or wider.
- Why does the calculator say my numbers are rounded?
- Because pixels do not come in fractions. A 1000-pixel-wide image at 16:9 wants to be 562.5 pixels tall, and neither 562 nor 563 is exactly 16:9. The difference is far too small to see, but a calculator that reported 562 as "exactly 16:9" would be lying about something it could easily be honest about.
- What is the difference between aspect ratio and resolution?
- Resolution is how many pixels there are; aspect ratio is what shape they make. 1920×1080 and 1280×720 are different resolutions and the same ratio — one is sharper, both are the same shape. A platform asking for 16:9 is describing the shape and usually specifies a minimum resolution separately.
- Which ratio should I use?
- Whichever the destination asks for; the table on this page lists what each standard ratio is actually used for. If nothing is asking, use the one your camera produced — 3:2 on most cameras, 4:3 on most phones — because that needs no crop at all.