About AspectCalc

Last updated: October 9, 2026.

AspectCalc is a free toolkit for calculating, checking, converting and understanding image, video and screen dimensions. It exists for one everyday problem: you have a width and a height, or a target shape, and you need to know what the other one should be before you export, crop, buy, upload or paste. Every tool on the site runs in your browser, and the arithmetic is shown rather than hidden.

Purpose of this site

AspectCalc exists to answer one question exactly: given a width and a height, or a target shape, what should the other number be? The answer has to be correct rather than merely convenient, so the site shows its arithmetic — the greatest common divisor it applied, the decimal it produced and the closest common ratio — instead of returning a label and asking you to trust it.

Everything here is free, runs in your browser and needs no account. The site is not a review site and does not recommend products; where a device appears on a page, it appears because its screen has a resolution and a ratio worth calculating against, and nothing more.

Update status

This page was last updated on October 9, 2026. The site is maintained on an ongoing basis rather than on a fixed schedule: pages are revised when a platform changes a recommended size, when a manufacturer publishes new specifications, when a reader reports an error, or when a ratio guide gains a new worked example or a clearer explanation.

Two rules govern the dates you see here. A page's stated update date changes only when that page actually changes — pages are never re-dated to look fresh. And device figures are re-checked against the manufacturer's published specifications when a new model arrives, rather than carried forward on the assumption that nothing has moved.

Corrections are welcome through the contact page, and the verification process described below explains how published numbers are checked before the site is built.

What the site covers

Four things get confused with each other constantly, so the site keeps them separate:

• Aspect ratio — the shape, written width:height. It says nothing about how big the picture is.
• Resolution — the pixel grid, written width × height. It says nothing about how big the screen is.
• Physical size — inches or centimetres, measured diagonally.
• Pixel density — pixels per inch, which is what connects the grid to the physical size.

Two screens can share a resolution and be different sizes. Two screens can share a ratio and be different resolutions. The aspect ratio calculator works on the first, the crop and pad converter works on what to do when the shape you have is not the shape you need, and the resize calculator changes the grid while holding the shape still.

Calculation methodology

Aspect ratio = width : height, reduced to the smallest whole numbers that describe the same shape. The reduction is a greatest-common-divisor division, not a lookup, so the answer is exact for any pair you type.

Worked example, 1920 × 1080:

• 1920 ÷ 1080 = 1.7778, the decimal form.
• The greatest common divisor of 1920 and 1080 is 120.
• 1920 ÷ 120 = 16 and 1080 ÷ 120 = 9, so the ratio is 16:9.

The GCD is found with Euclid's algorithm — 1920 mod 1080 = 840, 1080 mod 840 = 240, 840 mod 240 = 120, 240 mod 120 = 0 — which is why the result is the same whether you type the pair as landscape or portrait: the tool reduces first and reports the orientation separately.

Not every published resolution divides into a tidy pair. A panel of 2184 × 1968 reduces to 91:82, which is very close to 10:9 but is not 10:9. Where that happens the pages say so and give the exact reduction alongside the rounded label, because a wallpaper or a crop built on the round number will not land flush on the real panel.

Resolution and pixel density

Total pixel count is simply width × height: 1920 × 1080 is 2,073,600 pixels, a little over 2 megapixels; 4000 × 3000 is 12,000,000, or 12 megapixels. That figure tells you how much detail the file can hold, and nothing about how large it will look.

Pixel density connects the two. The diagonal in pixels is √(width² + height²), and dividing that by the diagonal in inches gives pixels per inch. A 1920 × 1080 panel has a diagonal of about 2203 pixels, so on a 24-inch screen that is roughly 92 ppi. The same 1920 × 1080 on a 6-inch screen would be about 367 ppi — same grid, far denser, which is why resolution alone never tells you how sharp something will look.

How the numbers are verified

The example figures on these pages are not typed by hand and left alone. A script recomputes every ratio, every decimal, every crop size and every device panel from its source pixel pair before the site is built, and the build fails if any published figure disagrees with real arithmetic. Reducing 2520 × 1080 to 21:9, or stating that a centred 9:16 column inside a 16:9 frame is about a third of the width, are both claims the script checks.

Device specifications are quoted from the manufacturer's published figures and attributed on the page. Where a manufacturer's own numbers do not divide evenly, or where two of a device's own screens differ from each other, that is stated rather than rounded away. Nothing on these pages comes from measurement we performed ourselves — if a page ever does, it will say so explicitly.

How the image tools handle your files

The image aspect ratio checker reads the file in your browser using the File and Image APIs. The image is never uploaded, never sent to a server and never stored; there is no server-side image handling to upload to, because the site is static. Closing the tab discards it. The crop calculator and resize calculator do not ask for a file at all — they take two numbers and give you the dimensions to use in whatever editor you already have open.

Why it is free

The site is supported by advertising rather than by subscriptions, so there is no account, no paywall and no limit on how many calculations you run. Nothing is gated behind signing in, and no calculator input is ever recorded.

Corrections and maintenance

Specifications change, platforms change their recommended sizes, and mistakes happen. If a figure looks wrong, a page is out of date, or a tool gives you an answer you can reproduce by hand as incorrect, please say so on the contact page — include the numbers you entered and what you expected, which is enough to reproduce any calculation here.

Corrections are made to the source content and rebuilt, and the page's stated update date changes only when the page actually changes. Pages are not re-dated to look fresh.

What this site is not

AspectCalc is a calculator and reference site. It does not review phones, monitors or cameras, and no page here is a buying recommendation. Where device screens appear — for example in the foldable phone aspect ratios pages — they appear only because a screen has a resolution and a ratio worth calculating against, and the pages stay strictly on dimensions, wallpapers and cropping.