Image Sizes: Platform Dimensions and Aspect Ratios
One page per canvas size and per aspect ratio, built from the same preset table the calculator uses. Each size page gives the exact pixels, the simplified ratio worked out by greatest common divisor, the megapixel count, why the platform chose that shape and which tool on this site produces it. Platform sizes are published guidance and they do change, so the ratio and the reasoning matter more than memorising the numbers.
Every page here embeds the Aspect Ratio Calculator. Enter a width and a height, or a ratio and one dimension, and it solves the missing one, simplifies the ratio, counts the megapixels and gives you a copyable CSS value.
42 pages in this section.
Kind Platform sizes
YouTube 1080p video size: 1920 by 1080
Why 1920 by 1080 is the standard full HD upload frame, what the player overlays cover, and how the thumbnail is a separate asset at the same shape.
YouTube 4K video size: 3840 by 2160
The 4K UHD frame at 3840 by 2160, why it is exactly four times the pixel count of 1080p, and what uploading above the watched resolution actually buys you.
YouTube Shorts size: 1080 by 1920
The 9:16 Shorts frame at 1080 by 1920, how it compares to the Stories and TikTok frame it shares pixels with, and where the interface covers your picture.
Instagram post size: 1080 by 1080
The 1:1 square post at 1080 by 1080, why the square survived the move away from it, and how it compares to the taller portrait frame in the feed.
Instagram Story size: 1080 by 1920
The full screen 9:16 Story frame, the interface that sits over its top and bottom edges, and how it differs from the feed formats in the same account.
Instagram landscape size: 1080 by 566
The widest frame the feed accepts, why 1080 by 566 simplifies to the awkward 540:283, and how it relates to the 1.91:1 link preview shape.
Instagram portrait size: 1080 by 1350
The 4:5 portrait feed frame at 1080 by 1350, why it takes the most screen height of any feed post, and what the profile grid crops away from it.
TikTok video size: 1080 by 1920
The 9:16 TikTok frame, the right hand action rail and bottom caption block that overlay it, and how it differs from Stories despite the identical pixels.
X and Twitter post image size: 1200 by 675
The 1200 by 675 timeline image, why 16:9 at this width is a comfortable retina size, and how the timeline can crop a taller image in the preview.
X and Twitter header size: 1500 by 500
The 3:1 profile banner at 1500 by 500, where the avatar overlaps it, and why a wide strip crops unpredictably between desktop and mobile.
Facebook post image size: 1200 by 630
The 1200 by 630 feed image, why it reduces to 40:21 rather than anything tidy, and why the same pixels serve as the standard link preview size.
Facebook cover photo size: 820 by 312
The cover photo at 820 by 312, why it reduces to the awkward 205:78, and how the desktop and mobile crops take different parts of the same image.
LinkedIn post image size: 1200 by 627
The 1200 by 627 feed image, why it is three pixels shorter than the 1200 by 630 link preview shape, and whether the difference is worth a separate export.
LinkedIn banner size: 1584 by 396
The profile banner at 1584 by 396, an exact 4:1 strip, where the profile photo overlaps it, and how much of the width a narrow screen removes.
Pinterest pin size: 1000 by 1500
The 2:3 pin at 1000 by 1500, why a portrait ratio wins in a masonry feed, and what happens to a pin that is taller than the recommended shape.
iPhone 15 Pro screen size: 1179 by 2556
The 1179 by 2556 device pixel resolution, the 393 by 852 layout size it corresponds to at three times scale, and why the ratio reduces to 131:284.
iPad Pro 12.9 inch screen size: 2048 by 2732
The 2048 by 2732 panel resolution, the 1024 by 1366 layout size at two times scale, and why 512:683 is close to but not exactly 3:4.
MacBook Pro 14 inch screen size: 3024 by 1964
The 3024 by 1964 panel, how the extra 74 pixels of height above a 16:10 rectangle account for the menu bar strip, and the layout size at two times scale.
1080p Full HD screen size: 1920 by 1080
The most common desktop display resolution, where the 1080p name comes from, and why device pixels and CSS pixels stopped being the same number.
1440p QHD screen size: 2560 by 1440
The 2560 by 1440 quad HD resolution, why quad refers to 720p rather than 1080p, and how it sits between Full HD and 4K in pixel count.
4K UHD screen size: 3840 by 2160
The 3840 by 2160 UHD resolution, why it is named for a width it does not have, how it differs from cinema 4K, and what it costs to process.
Ultrawide screen size: 3440 by 1440
The 3440 by 1440 ultrawide panel, why its true ratio is 43:18 rather than the advertised 21:9, and how it relates to a QHD display.
A4 at 300 DPI: 2480 by 3508 pixels
How 210 by 297 millimetres becomes 2480 by 3508 pixels at 300 DPI, why the A series ratio is the square root of two, and what bleed adds.
US Letter at 300 DPI: 2550 by 3300 pixels
How 8.5 by 11 inches becomes exactly 2550 by 3300 pixels at 300 DPI, the 17:22 ratio it reduces to, and why it does not interchange with A4.
Business card at 300 DPI: 1050 by 600 pixels
The 1050 by 600 pixel card canvas, the 3.5 by 2 inch physical size behind it, the 7:4 ratio, and the bleed and safe margins a printer expects.
OG image size: 1200 by 630
The 1200 by 630 open graph image, why it became the default sharing size, the markup that nominates it, and the rules that make it actually appear.
Favicon at 512 by 512
The 512 by 512 icon canvas, why a favicon is a set of sizes rather than one file, and exactly which outputs the favicon generator here produces.
iOS app icon size: 1024 by 1024
The 1024 by 1024 app icon master, why the corners should be left square, why transparency is a problem, and how the smaller sizes derive from it.
Kind Aspect ratios
16:9 aspect ratio
Where the 16:9 ratio came from, the pixel dimensions that hit it exactly, what it suits, and the places where a widescreen frame is the wrong shape.
4:3 aspect ratio
The 1.333 ratio that ran television and computer monitors for decades, where it still appears today, and how it compares to the widescreen shapes.
1:1 aspect ratio
The square ratio, its origins in medium format film and social feeds, why it is the most reusable shape, and where it wastes space.
21:9 aspect ratio
The 21:9 marketing label at 2.3333, the 43:18 and 64:27 shapes that real ultrawide panels actually use, and how to design for the gap between them.
9:16 aspect ratio
The vertical video ratio at 0.5625, its exact inverse relationship with widescreen, and why modern phone screens are taller than it.
3:2 aspect ratio
The 1.5 ratio inherited from the 35mm film frame, the sensors and laptop screens that still use it, and how it sits between 4:3 and 16:9.
2:3 aspect ratio
The portrait form of the 35mm frame at 0.6667, why it is the recommended shape in masonry feeds, and how it compares to 4:5 and 9:16.
5:4 aspect ratio
The 1.25 ratio behind 1280 by 1024 monitors and 8 by 10 inch prints, why it caused distorted desktops for years, and where it still applies.
32:9 aspect ratio
The super ultrawide ratio at 3.5556, exactly double 16:9, the panels that use it, and why a layout at this width needs columns rather than wider text.
2.39:1 aspect ratio
The widescreen cinema ratio at 2.39, why it used to be 2.35, how anamorphic lenses produced it, and what it means for a video framed this way.
What is an aspect ratio?
Aspect ratio is width divided by height, and it says nothing about resolution or file size. How to simplify one, read it as a decimal, and use it correctly.
The CSS aspect-ratio property
How the aspect-ratio property works, what happens when a width and a height are also set, and how it removes layout shift when media loads.
Letterboxing versus cropping
What happens when an image does not match its frame: bars that keep everything, or a crop that discards the edges. How object-fit chooses between them.
DPI versus pixel dimensions
Why a raster file only stores pixels, what the DPI number in its metadata does and does not change, and how to work out a print size from a pixel count.