Aspect Ratio Calculator – Calculate Width & Height Instantly
Calculate matching width and height for any aspect ratio, then preview how your image or video fits.
Pick a ratio or size preset, then edit width or height — the other updates instantly.
A Free Aspect Ratio Calculator for Images, Screens & Video
This aspect ratio calculator lets you calculate aspect ratio online in seconds — enter a ratio and one dimension to get the other, in pixels or inches, or pick a common ratio like 16:9 or 4:3 and let it do the math. It works as a simple aspect calculator for photos, displays, and video, with no signup and no limits on how many times you use it.
How the Aspect Ratio Calculator Works
Type a width or height and this aspect ratio calculator instantly fills in the other side, keeping your chosen ratio locked. Prefer to work the other way? Enter your ratio directly as two numbers and the calculator generates matching dimensions at any size. Every result updates live, so there's no separate 'calculate' button to click — just an aspect ratio cal that reacts as you type, whether you're entering pixels for a design file or inches for print.
16:9 Aspect Ratio Calculator, 4:3 Aspect Ratio Calculator, and More
Not sure what ratio you need? Use the built-in aspect ratio generator to jump straight to standard formats. As a 16:9 aspect ratio calculator, it covers the most common widescreen and video standard; as a 4:3 aspect ratio calculator, it handles the classic photo and older TV format. Square (1:1), ultrawide (21:9), and other presets are one click away too. The same engine works as a display aspect ratio calculator: plug in a monitor or TV resolution and it doubles as an aspect ratio resolution calculator, showing you exactly how that screen's width and height relate.
The Aspect Ratio Formula, Explained
Aspect ratio is simply width compared to height, written as width:height. To find it, divide both numbers by their greatest common divisor until they can't be simplified further. For example, a 1920×1080 image: the greatest common divisor of 1920 and 1080 is 120, so 1920÷120 = 16 and 1080÷120 = 9 — giving the ratio 16:9. This calculator applies that same formula automatically whenever you enter a width and height, or a ratio and one dimension, so you never have to work out the division yourself.
One Calculator for Photos, Designs, and Displays
Whether you're sizing an image for print, matching aspect ratio dimensions for a video export, or acting as a quick image size calculator ratio for a design mockup, this tool adapts to the input you give it. It's built to work as an aspect ratio calculator for images just as easily as for pure numbers — no separate mode needed.
Already Know Your Width and Height?
If you have two dimensions and want the ratio instead of calculating from one, the Aspect Ratio Finder does that in reverse — enter width and height and get the simplified ratio back, or even detect it straight from an uploaded photo or video.
Frequently asked questions
Common questions about the Aspect Ratio Calculator.
What is aspect ratio?
Aspect ratio is the proportional relationship between an image, screen, or video's width and its height, written as width:height (for example, 16:9). It describes shape, not size — a tiny phone screen and a huge cinema screen can share the same aspect ratio even though their actual dimensions are completely different.
How do you calculate aspect ratio?
Divide the width and height by their greatest common divisor until neither can be simplified further. This calculator does that automatically — enter a width and height and it returns the simplified ratio instantly, or enter a ratio and one dimension to get the matching size back.
What is the formula for aspect ratio?
The formula is width : height, simplified by dividing both numbers by their greatest common divisor. For a 1920×1080 image, the greatest common divisor of 1920 and 1080 is 120, so 1920÷120 = 16 and 1080÷120 = 9 — giving an aspect ratio of 16:9.
How do I find my aspect ratio?
It depends what you're starting with. If you already have an image, video, or a set of dimensions and want to identify the ratio, use the Aspect Ratio Finder. If you already know the ratio and need the matching width or height, use this calculator.
What aspect ratio is 1920×1080?
1920×1080 simplifies to 16:9, the standard widescreen ratio used by Full HD video, monitors, and most streaming content.
Is 1280×720 a 16:9 aspect ratio?
Yes. 1280×720 (HD, or 720p) simplifies to 16:9, the same ratio as 1920×1080 — just a lower pixel resolution at the same shape.
Is 1024×768 a 16:9 aspect ratio?
No. 1024×768 simplifies to 4:3, the older near-square format used by classic TVs and monitors — not the 16:9 widescreen ratio.
What aspect ratio is 1080×1350?
1080×1350 simplifies to 4:5, the portrait ratio Instagram recommends for feed posts to maximize vertical space in the mobile feed.
What is the difference between 4:3 and 16:9 aspect ratio?
4:3 is the older, nearly square format used by classic TVs and early digital photos. 16:9 is the modern widescreen standard used by almost all current video, streaming, and monitors. A 4:3 image looks noticeably taller and narrower side-by-side with the same content in 16:9.
What does a 2.39:1 aspect ratio mean?
2.39:1 (sometimes shown as 2.40:1) is an ultra-widescreen cinematic ratio, often called CinemaScope, used for theatrical film releases. It's significantly wider than standard 16:9 video, which is why movies formatted this way show black letterbox bars on a regular widescreen TV.
What aspect ratio does Instagram use?
The most common recommended ratio for Instagram feed posts is 4:5 (portrait), with 1:1 (square) also supported. Stories and Reels typically use 9:16 (vertical). This calculator's social preview shows how an image or video fits each format before you post.
What aspect ratio do YouTube and YouTube Shorts use?
Standard YouTube videos typically use 16:9 widescreen. YouTube Shorts use 9:16, the same vertical format as Instagram Reels and TikTok, designed for full-screen viewing on a phone.
What aspect ratio does TikTok use?
TikTok videos are typically formatted at 9:16, a tall vertical ratio built for full-screen mobile viewing — the same format commonly used by Instagram Reels and YouTube Shorts.