Aspect ratio and crop
Most ratio calculators tell you the ratio. The questions that matter are what gets cut off and what the app covers, so this shows you both.
Resizing and cropping are not the same operation
They get talked about interchangeably, and the difference is whether you lose part of the picture. One is safe and one always costs something.
Resize keeps the shape
A 3840×2160 photo resized to 1920 wide becomes 1920×1080. Same ratio, same framing, fewer pixels. Nothing is lost except resolution, and scaling down is always safe.
Crop changes the shape, so something goes
The same image into a 4:5 Instagram post cannot keep its framing, because 16:9 and 4:5 are different shapes. Roughly 60% of the width has to be discarded. The only question is which 60%.
That is what the anchor is for, and it is where the visible mistakes come from. A centre crop is the default everywhere and it is wrong for a headshot, because faces sit in the upper third and centring cuts the top of the head off. Anchor to the top for portraits, to the bottom for landscapes with a lot of sky.
How much a crop actually costs
The percentage kept is worth watching, because the numbers are worse than they feel:
- 16:9 into 1:1 square
- Keeps about 56%. Nearly half the frame gone.
- 16:9 into 4:5 Instagram post
- Keeps about 45%. More than half gone.
- 16:9 into 9:16 story
- Keeps about 32%. This is why reformatting landscape video for stories rarely works.
- 3:2 into 4:3
- Keeps about 89%. A mild change of shape and usually fine.
- 3:2 into 4:5
- Keeps about 53%. Landscape into portrait is always a severe crop, whatever the numbers look like: you are turning the picture on its side.
Below roughly half, cropping stops being a fix. Reframing or shooting for the target ratio in the first place is the real answer, which is why anybody shooting for social shoots vertical.
The third question: what will the app cover
Getting the ratio right is not the end of it. A 9:16 export is never seen as a clean 9:16 rectangle, because every vertical video app draws its own interface on top: the username and sound label across the top, the caption and call to action across the bottom, and a column of buttons up the right hand side.
On TikTok that interface covers about 44% of the frame. Compose a shot that is perfectly cropped and put the subject in the lower third, and the caption block sits on top of it. That is the same mistake as cropping a head off, discovered one step later.
These are guides, not specifications
No platform publishes an exact safe area, and the overlays shift with app version, caption length, device notch and whether the viewer has expanded the description. Community figures disagree, sometimes badly: published safe areas for YouTube Shorts alone include 888 by 1500, 1080 by 1420 and 1080 by 1350 on the same 1080 by 1920 canvas.
So rather than pick one and present it as fact, each platform here carries a note about how well its figures agree, and the least agreed-upon of the three says so on screen. Check a real preview in the app before posting. The value of the overlay is catching the obvious mistake early, not certifying the last twenty pixels.
Terminology
- Aspect ratio
- Width relative to height, reduced. 3840×2160 and 1920×1080 are both 16:9.
- Anchor
- Which part of the source survives a crop. Nine positions, centre by default.
- Crop geometry
- Four numbers describing the surviving rectangle: width, height, and how far across and down it starts.
- Upscaling
- Enlarging past the original. Invents pixels that were never captured, so the result is always softer than the source.
- Safe zone
- The part of a vertical video that the app's own interface does not cover. Everything outside it risks sitting behind a caption, a button or a progress bar.
Questions about ratios and cropping
What is the difference between resizing and cropping?
Resizing keeps the shape. A 3840×2160 image resized to 1920 wide becomes 1920×1080. The ratio is identical, nothing is lost, the pixels are just smaller.
Cropping changes the shape, so something always goes. Putting that same 16:9 image into a 4:5 Instagram post means cutting roughly 60% of the width away.
Confusing the two is why a photo sent to a 16:9 slot comes back with somebody's head missing. If the target ratio differs from the source ratio, you are cropping, whatever the button was labelled.
How do I work out the aspect ratio of my image?
Divide the width by the height, then reduce it. 3840 ÷ 2160 is 1.777…, and 3840:2160 reduces by a common factor of 240 to give 16:9.
This does the reduction for you and shows both forms, because some ratios are only useful as a decimal. An Open Graph card is 1200×630, which reduces to 40:21 — technically correct and no help to anybody. As a decimal it is 1.905:1.
Which crop anchor should I use?
Whichever keeps the subject. The default centre crop is right surprisingly often and wrong in two common cases.
For a portrait or headshot going into a wide frame, anchor to the top — faces sit in the upper third and a centre crop cuts the forehead. For a landscape with sky, anchor to the bottom to keep the ground rather than empty sky.
What are the standard social media ratios?
Instagram: 1:1 square, 4:5 portrait post, 9:16 for stories and reels. 4:5 is the one to design for, since it takes the most vertical space in the feed.
X: 16:9 for post images, 3:1 for the header. LinkedIn: 1200×627. YouTube thumbnails: 1280×720, which is 16:9. Open Graph link previews: 1200×630.
All of them are presets here so you do not have to remember any of it.
Can I enlarge an image without losing quality?
No. Enlarging invents pixels that were never captured, so the result is softer than the original no matter what tool does it. The tool warns you when the target is bigger than the source.
Scaling down is safe and always has been. If you need a larger image, the fix is to go back to the original file rather than to the export you already shrank.
What is that geometry string in the output?
ImageMagick crop notation: width x height + x offset + y offset. So 1200x675+0+371 means take a 1200 by 675 region starting 0 across and 371 down.
It pastes straight into an ImageMagick or GraphicsMagick command, and the same four numbers are what most editors and image libraries want when you set a crop by hand.
Why does cropping to a square lose so much?
Because a square is a long way from most source shapes. A 16:9 photo cropped to 1:1 keeps only about 56% of the image; a 9:16 vertical video cropped to square keeps the same fraction the other way.
The percentage is shown for exactly this reason. Below about half, it is usually better to reframe or reshoot than to salvage the crop.
What is a safe zone, and why is my text getting covered?
Because a vertical video is not seen as a bare 9:16 rectangle. TikTok, Instagram Reels and YouTube Shorts all paint their own interface over the top of it: username and sound label along the top, caption and call to action along the bottom, and a column of like, comment and share buttons up the right.
On TikTok that interface covers roughly 44% of the frame. Anything important placed there is simply not visible, which is the same failure as cropping somebody's head off, just one step later in the process.
What are the safe zone dimensions for TikTok, Reels and Shorts?
On a 1080 by 1920 canvas, the commonly quoted insets are: TikTok about 140 px clear at the top, 400 at the bottom, 60 left and 180 right. Instagram and Facebook Reels about 220 top and 420 bottom, leaving a 1010 px wide column. YouTube Shorts roughly 120 top, 300 bottom and 120 right.
Treat all of these as a guide rather than a specification. No platform publishes an exact safe area, and the overlays move with app version, caption length, device notch and whether the viewer has expanded the description.
How reliable are these safe zone numbers?
They vary, and the tool says which ones vary most rather than presenting all three as equally solid. The TikTok figures are quoted consistently across independent guides. The Reels figures come from fewer sources but are internally consistent.
The Shorts figures disagree considerably: published safe areas for the same platform include 888 by 1500, 1080 by 1420 and 1080 by 1350. So the Shorts overlay carries a warning, and the honest advice for any of the three is to check a real preview in the app before posting.
Does this upload my image?
There is no image involved. You type in the dimensions and it works with numbers, which means nothing to upload and nothing to wait for.
The preview is a scale drawing of your dimensions, not your photograph.
Notes
Ratios are reduced with a greatest common divisor, and shown as a decimal instead once a reduced form stops being readable. 1200×630 reduces to 40:21, which is accurate and useless; 1.905:1 is the number people can work with.
The safe zone insets are the figures quoted consistently across published creator guides, measured on a 1080×1920 canvas and scaled proportionally to whatever size you enter. They are not official: no platform publishes an exact safe area, and sources disagree, most of all on YouTube Shorts. Each platform carries a note about how well its figures agree, and the overlay is there to catch an obvious composition mistake, not to certify the edge.
Platform dimensions and interface layouts change when platforms change them. If a preset or a safe zone here is out of date, tell me and it gets corrected.