What Is My Aspect Ratio
Instantly check your screen's aspect ratio (like 16:9) computed from screen.width and screen.height and reduced by their greatest common divisor. See the simplified ratio, raw resolution, and decimal value, plus a built-in calculator to reduce any width × height. Detected locally in your browser — nothing is stored.
Ratio Calculator
Reduce any width × height
How to use this tool
Read Your Ratio
On load, the tool detects your screen resolution and shows the simplified aspect ratio (e.g. 16:9) big and clear.
Check the Details
See the raw pixel resolution and the decimal ratio (width ÷ height) beside the headline value for precise comparison.
Reduce Any Size
Use the sidebar calculator to enter any width and height — an image, video, or custom size — and get its GCD-reduced ratio.
If your ratio looks odd (like 683:384), trust the decimal value — anything near 1.778 is effectively 16:9. Scaling and browser zoom can stop a resolution reducing cleanly.
Your screen size is detected locally in your browser and never leaves your device — nothing is uploaded or stored. The ratio recomputes automatically if you resize the window or move it to another display.
Find Your Screen's Aspect Ratio in One Glance
An aspect ratio describes the relationship between a display's width and its height, written as two numbers separated by a colon — like 16:9. This aspect ratio checker reads your screen's resolution the moment the page loads, reduces it to its simplest form, and shows the result big and clear, along with the raw pixel resolution and the precise decimal ratio. There's nothing to install and nothing to configure: open the page and your ratio is already on screen.
What the Aspect Ratio Actually Means
The ratio tells you the shape of your display independent of its size. A 24-inch and a 32-inch monitor can both be 16:9 — they hold the same proportions, just at different pixel counts. The first number is the relative width, the second the relative height. So 16:9 means that for every 16 units across, there are 9 units down. That shape is what determines whether a video fills your screen edge-to-edge or shows black bars, and whether a design built for one display looks right on another.
How the Number Is Calculated
The math is simple but precise. The tool takes your screen's width and height in pixels and divides both by their greatest common divisor (GCD) — the largest number that divides into both evenly. For a 1920×1080 display the GCD is 120, so the ratio reduces to 1920÷120 : 1080÷120 = 16:9. Alongside that, the decimal ratio (width ÷ height) is shown — 1.778 for 16:9 — which is the most reliable value when your resolution doesn't reduce to a tidy pair. Common shapes include 16:9 (widescreen HD), 16:10 (taller widescreen, popular on laptops), 4:3 (classic), 21:9 (ultrawide), and 1:1 (square).
Why You'd Want to Check It
Knowing your aspect ratio is genuinely useful in several workflows:
- Designers and developers match layouts, hero images, and CSS breakpoints to real-world screen shapes, and test how a responsive page behaves at different ratios.
- Video editors and streamers export at the correct ratio so footage fills the frame without letterboxing or cropping.
- Gamers confirm whether a title supports their ultrawide or 16:10 panel before tweaking field-of-view settings.
- Anyone buying a monitor or TV can compare the shape of a new display against what they already use.
It Recomputes as Things Change
Because the value is read live, the ratio updates automatically when you resize the browser, change your display scaling, or drag the window onto a second monitor with a different resolution. You always see the ratio for the display you're actually looking at, not a stale snapshot from page load.
A Built-In Ratio Calculator
Beyond your own screen, the sidebar includes a small ratio calculator: type any width and height — for an image, a video frame, a print size, or a hypothetical resolution — and it returns the GCD-reduced ratio and decimal instantly. It's a quick way to check whether a 1280×800 asset is 16:10 (it is) or to find the shape of an unusual custom size.
Built for Privacy
All detection and math happen locally in your browser using JavaScript. Your resolution and computed ratio are never uploaded, logged, or stored — there's no server round-trip at all. That makes it safe to use on any device without sharing anything about your hardware. If you're inspecting other technical details about your setup, pair this with the JSON formatter for cleaning up config files, or check your screen resolution for the full pixel breakdown.