Aspect Ratio Calculator

Match Your Platform

YouTube? 16:9 (1920x1080). Instagram feed? 1:1 or 4:5. TikTok? 9:16 vertical. Each platform has a preferred ratio, and if you don't match it, your content gets cropped automatically. Save yourself the headache.

Higher Resolution ≠ Better Quality

A 3840x2160 image looks great, but if you're uploading to Instagram, it gets compressed anyway. Start with the right aspect ratio, then worry about resolution. Ratio first, pixels second.

Don't Crop Center by Default

Most editing tools crop from the center when you change aspect ratios. If your subject isn't perfectly centered, they'll get cut off. Always preview the crop before exporting.

Confusing Ratio with Resolution

Aspect ratio is about proportions, not size. 1920x1080 and 3840x2160 are both 16:9. Same ratio, different resolution. People mix these up all the time.

Why it happens: The terms sound technical and get used interchangeably (incorrectly).
How to avoid: Ratio = shape. Resolution = detail. Two different things.

Using Desktop Ratios for Mobile

A 16:9 video might look great on a laptop, but on a phone held vertically? You're staring at a tiny rectangle with black bars above and below. Design for where people will actually watch.

Real consequence: Your content gets scrolled past because it's awkward to view.
Fix: Check your analytics. If 70% of viewers are on mobile, make vertical content (9:16).

Forgetting About Pixel Perfect

You can't have a screen that's 1920.5 pixels wide. But this calculator might give you decimals if you pick weird ratios. Always round to whole numbers for actual screens.

How to avoid: This calculator rounds automatically. But if you're working in Photoshop or code, double-check your final numbers are integers.

What is aspect ratio and why does it matter?

Aspect ratio is the width-to-height proportion of an image or screen, expressed as two numbers (like 16:9). It matters because if you change one dimension without maintaining the ratio, your content gets stretched or squashed. Ever see those old 4:3 TV shows stretched to fill a widescreen? That's what happens when you ignore aspect ratios.

What aspect ratio should I use?

Depends what you're making. For YouTube videos and modern TVs, use 16:9 (1920x1080). For Instagram posts, 1:1 (square) or 4:5 works best. Ultrawide monitors are 21:9. Old-school content was 4:3. There's no 'wrong' ratio - just match what fits your platform.

How do I calculate aspect ratio from width and height?

Divide both numbers by their greatest common divisor (GCD). For example, 1920÷1080: the GCD is 120, so you get 16:9. Or just use this calculator - it handles the math instantly. Type in any width and height, and you'll see the simplified ratio.

What if I know the width but need the height?

That's exactly what this calculator does. Set your desired aspect ratio (like 16:9), enter your width, and it automatically calculates the correct height. Same works in reverse - enter height to get width. No manual math needed.

Can I use non-standard aspect ratios?

Absolutely. This calculator works with any ratio you type in - 2.35:1 for cinema, 16:10 for some laptops, even weird stuff like 17:11 if that's what you need. Just change the ratio numbers and your dimensions will update automatically.